Nyax is a unique character in the world of Star Wars for several reasons. not one of which he looks like a monster made real. He has a complicated backstory, both in-verse and out, and became an immensely strong adversary for Luke and Mara Jade Skywalker. He also happens to be one of the most misunderstood characters because of the nature of some of his feats dealing with a Force wellspring that amped his powers. Hopefully this thread will shed some light on the subject.

This thread will be divided into the following categories:

• Power
• Physicals/Augmentations
• Weakness
• Force Powers
• Lightsaber and Combat Skill

Power

The plot synopsis on the back of Rebel Stand implies Nyax is the only thing preventing the Yuuzhan Vong from taking control of Coruscant and when Luke and Mara Jade Skywalker confront him they are thrust into a "fierce battle for their lives" with the chances of escaping nearly impossible:

On Coruscant, Luke and Mara Jade Skywalker have made a shocking discovery that is preventing the Yuuzhan Vong from exerting complete control. But when the enemy tracks them down, Luke and Mara are thrust into a fierce battle for their lives. Suddenly, the chances of escaping appear nearly impossible.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand plot synopsis

The fight between Nyax and Luke Skywalker, Mara Jade Skywalker, and Tahiri Veila is described as a "tremendous Force battle":

A chilling vision of the dark side brought Luke to the heart of the Yuuzhan Vong-held Coruscant. In the depths of the altered city planet, Luke faced off against Lord Nyax, the deranged mutated Dark Jedi that once was Irek Ismeren.

Surviving a tremendous Force battle at the site of the old Jedi Temple, Skywalker concentrated his efforts on restarting the Jedi Council.

Source: Star Wars Databank (Old)

Nyax was a "powerful dark-side enemy" who was "enhanced to possess incredible dark-side energies" and needed the "combined Force skills" of Luke Skywalker, Mara Jade Skywalker, and Tahiri Veila to defeat him:

In the days that followed, Mara and Luke made preparations to return to Coruscant, where Luke believed a new and powerful dark-side enemy had emerged. Once there, they began to hear rumours of a mysterious entity that people were referring to as Lord [Nyax]. This was the name of a galactic 'bogey man' with whom parents had frightened their children over the centuries.

Upon further investigation, they learned that this figure was in fact a tall and enigmatic human male, who had been genetically altered and technologically enhanced to possess incredible dark-side energies. Only the combined Force skills of Luke, Mara and a young Jedi called Tahiri were able to bring this new and deadly foe down.

— The Official Star Wars Fact File 57

Nyax's mother kept a close watch on him as he "grew" and planned to train him to be the most powerful Dark Jedi ever:

"It appears that after leaving Belsavis, he and his mother came to Coruscant and hid here . . . and by 'here' I mean in this very facility. His mother carefully monitored his progress in the Force, training him so that he'd be the most powerful Dark Jedi in existence, and gave him medical treatments to make him much bigger, more imposing, more physically powerful. She also arranged to bring in the ysalamiri to keep him hidden as his presence in the Force grew stronger."

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Nyax's power makes Luke Skywalker have a vision of "tremendous dark side evil":

Luke found himself surrounded by foliage and thought for an instant that he was on foot patrol in Borleias's jungles. But he realized within an instant that the air here was even darker than was customary on Borleias, and the precise nature of the plants and trees around him was wrong for that world. Here, the trees were darker, larger, their limbs drooping, while opaque pools of groundwater concealed furtive movements of their occupants.

Dagobah. It was the world where he had trained with Yoda, a lifetime ago.

So this was a dream. He shook his head. No, in dreams he was not usually so lucid. It was a vision, then, a vision through the Force.

He turned and faced the opening into the cave. It was there that he had confronted a vision of Darth Vader—of himself in Vader's distinctive dress. Now, there was no Yoda to warn him against taking weapons into this place of evil and confrontation, and Luke felt sad that this vision would not give him even the momentary pleasure of seeing his old Master again in the one context where his presence was appropriate.

Luke found he was dressed in black. His lightsaber hung at his waist. He removed it, depositing it in the crook of a tree branch, and entered the cave.

Within, he found only darkness and silence. But he knew something was there, a few steps from him, a deeper darkness. He could neither see nor hear it, but he could feel it within the Force. He stepped toward it and felt it move to the side, circling him.

Then it brushed past him, a contact that sickened him, reawakened in him every great hatred of his life—for Darth Vader, for the Emperor, for himself when he had stumbled too far down the path of the dark side—and left the cave. Luke followed.

He emerged into brighter light than he'd seen outside a moment ago, and now he was surrounded by soaring buildings, construction so high that the sky was visible only as a faint sliver of light. All around him, duracrete surfaces, crashed landspeeders, and giant blocks of unrecognizable debris were coated with green algae and waving grasses in a more pallid green hue. At his feet, a human body was covered with the same stuff.

The darkness he'd pursued was ahead of him, farther down the narrow aperture between skyscrapers, still invisible to the naked eye, still nauseatingly tangible within the Force.

It roiled and spun like a tornado. It increased in size until it brushed against the buildings to either side. The algae and grasses there changed when it touched them, suddenly bearing large, malformed fruits as black and slick as old oil. Then every surface in sight was covered with the fruits, and as he watched they began to drop from their stems. They struck the ground and then struggled to newly developed feet, walking in every direction with the awkwardness of babies.

And each of them was filled with misery and dark side longing for ruin.

One opened its mouth and let out a piercing wail. Then another did, and a third. Suddenly the air was full of their cries.

A hand gripped Luke's shoulder. He opened his eyes. Mara was shaking him; her face was pale. The air was still filled with cries, but they were Ben's, and Mara held the baby away, as if to protect him from Luke. "What is it?" she asked.

"A vision." Luke brought his breathing under control and found that one part of his vision still lingered; dark side energy and malice still surrounded him. Ben, as sensitive to the Force as only the child of two eminent Jedi could be, wailed in protest. "There's evil on Coruscant. Tremendous dark side evil."

Source: The New Jedi Order - Enemy Lines I: Rebel Dream

Luke Skywalker felt he needed to leave Borleais and head to Coruscant to deal with the growing darkness he sensed, which was Nyax. Luke said the visions were getting worse and growing more frequent with a sense of urgency behind them. Coruscant had just been conquered by the Yuuzhan Vong but still the power Luke sensed made him adamant on wanting to go there to deal with it:

"You're going to do what?" Mara asked. Her voice had not risen to carry through the doors and into the conference room, but it had become sharper. It was loud enough to startle Ben, but the baby merely looked up from her arms, gurgled, looked at Luke, and reached out for his father. Luke gave him the pinkie of his natural hand to grasp.

Luke steeled himself. "I'm going to Coruscant."

"Your visions?"

"They're getting worse and more frequent. Whatever is happening there, it's building. Getting stronger. Or going to build, going to get stronger—I don't know if I'm seeing the present or the future."

"Or the past. You could be seeing something about Palpatine's rise to power."

He shook his head. "There wouldn't be a sense of urgency to the visions."

Source: The New Jedi Order - Enemy Lines I: Rebel Dream

Luke Skywalker, Mara Jade Skywalker, Tahiri Veila, and even the semi-trained Danni Quee all sense a "distant wrongness in the Force" from Nyax:

As his group entered a long gallery that had once been flanked by stores and emporiums, Luke again felt a twinge, some distant wrongness in the Force. The sensation had come to him before and he had steered toward it, hoping that it was the source of the unease, the visions that had brought him to Coruscant on this mission. But his fellow Jedi had not always seemed to share his perceptions.

He glanced at them. Mara was already looking his way, nodding. Tahiri stared off into the distance, in the direction of the twinge, alert as a hunting beast.

Even Danni was gazing in that general direction, a hint of confusion evident even through her Yuuzhan Vong makeup. "Did any of you feel something?" she asked.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Luke Skywalker senses Nyax as a "beacon of darkness":

Luke found he could sense the man in the Force—could do so without even reaching out for him. The man was a glowing light in the Force, a beacon in the midst of darkness. A beacon of darkness . . . but that suddenly didn't matter.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Luke Skywalker even believes that his team might not have enough resources to stop Nyax:

Bhindi fixed Luke with a grave look. "Besides, I suspect that you're not going to let that thing keep walking around out there. Are you?"

"I hope not." Luke looked up the hole; only a few meters of the water and atmosphere pipes were visible in the dim light from their glow rods. "It's very strong, very evil. And I have no idea whether we have enough resources here to stop it."

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Nyax fights and defeats a Yuuzhan Vong hunting party and two diseased voxyn. He starts the fight off by killing a voxyn by smashing its body with a large piece of machinery and then cuts the remaining warriors and voxyn to pieces:

She heard the voxyn's hisses go from excited to ferocious, heard their handlers call after them as they yanked leashes free from the handlers' grips.

"Jeedai!" called one of the warriors. "Now you die!"

Viqi heard the distinctive snap-hiss of a Jedi lightsaber igniting. One point on the far wall of the manufacturing chamber and the ceiling above it were illuminated by red light—moving light. The claws of the voxyn scrabbled as they charged for their prey.

Then there was another snap-hiss, and another, and another. The distant red glow brightened. Viqi saw the silhouette of a voxyn leaping high, vaulting intervening machinery, backlit by the glow—and then something rose to meet the voxyn in mid-flight.

It was not a Jedi, not a lightsaber blade. A block of machinery two meters on a side flew up from below and crashed into the leaping voxyn, striking with such force that Viqi heard the creature's bones shatter. The impact smashed the voxyn back through the air, a wobbly caricature of a once-living beast. The voxyn's body crashed onto the factory's duracrete floor and the block of machinery landed upon it, breaking more bones, and stuck there, not bouncing or rolling forward as it should have.

"Forward," Denua Ku said. He whipped his amphistaff free from his waist and charged after the other Yuuzhan Vong warriors, who now howled in rage and anticipation.

Viqi took two steps in Denua Ku's wake and then something crashed into her, took her from her feet, slapped her to the duracrete.

It was not a physical thing. It was despair and hatred, loathing and worthlessness, fear and howling rage. It was as though Viqi had spent every one of her years packing all the hateful emotions an ordinary person felt into a storeroom—and suddenly all the pressure had burst through the door and swept her away. She could only lie there, her arms and legs twitching outside her control, her stomach rebelling, her heart hammering inside her.

She heard the howl of the second voxyn, heard the ripping noise of the creature vomiting its acid at its prey. Then there was the sound of lightsabers swinging, hacking. Meat in great quantities slapping down onto the duracrete.

Viqi writhed in time with the war cries of the Yuuzhan Vong and, one by one, she heard them die under the almost musical tones of the lightsabers.

Then there was only the sound of lightsabers cutting, and cutting, and cutting.

The emotional agony that had gripped Viqi lessened—only a little. She managed to roll over onto her stomach and slowly, painfully came upright.

She knew the beings on the other side of the chamber had just killed everything that had entered the chamber with her. She wanted nothing more than to charge at them, to rip them to pieces with her bare hands.

But as she stood, some faint instinct of self-preservation rose within her, and one thought made up of words emerged: Run, or die.

She turned toward the doorway, and lurched out toward the light.

As she reached the doorway, she put her hand out to steady herself against the metal door that had once protected the factory's interior. It fell away from her grip, crashing down onto the duracrete with a tremendous clang.

The lightsabers in the distance switched off. Viqi froze. She waited, ears straining at the sudden silence.

Then she heard it, the padding of feet coming her way.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

During the fighting, Nyax released such a powerful wave of dark side energy that human Senator Viqi Shesh was physically knocked over and stuck in a fetal position for the whole fight. She described the feeling as if she spent all of her years packing all of the hateful emotions a person could feel into a room and then having it burst at once and carrying her away.

Elsewhere on Coruscant/Yuuzhan'tar, Luke Skywalker, Mara Jade Skywalker, Tahiri Veila, and even Danni Quee had all felt the powerful burst of energy Nyax released when fighting the Yuuzhan Vong hunting party. Luke felt "saturated" with a desire to kill every living thing in his vicinity, and Tahiri felt worse than after her torturing and conditioning from the Yuuzhan Vong and even admits that if the attack had been directed at her, it would have taken control of her:

Luke came awake and rose in a single smooth motion.

He didn't have to ask if Mara had felt it, too. She was awake, gripping her lightsaber, ready to ignite it.

Luke stepped out into the corridor. It was dimmed for sleeping, but Danni, too, was emerging, and Tahiri, who had been on guard in the corridor as the others slept, stared into one wall, through the wall, at something that was far away and toward the ground. "It's there again," she said, her voice faint.

Luke took a few deep breaths. He couldn't remember what he had just been dreaming—only that, for a moment, he had been filled, even saturated, with a desire to rise and kill every living being thing in his vicinity. Absurdly, he still felt loathing and contempt for his companions, for his wife, but as his mind and memory struggled to assert themselves, those emotions began to fade. "What did you feel?" he asked.

Tahiri shook her head, and Luke could finally see the lone tear flowing down her farther cheek. "Awfulness," she said. "More awful than when I was coming out of my conditioning and started to figure out what I'd almost become. It was all through me, through the Force. It almost had control of me. I think maybe it could have had control, if it had known I was here." The despair in her voice was heartbreaking.

None of the Wraiths had emerged from their new quarters. That made sense. This was a Force sending, a Force problem, and the Wraiths, largely oblivious to the Force, were not troubled.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Tahiri says that the sensations she felt from Nyax killing the Yuuzhan Vong hunting party felt like "jumping into an ocean of the dark side":

"Dark Jedi might be able to impose their will on normal people," Tahiri said. She had her arms crossed, and Luke suspected her pose was an effort to keep herself from trembling. "But not on fully trained Jedi. This was like jumping into an ocean of the dark side of the Force. It was like feeling Anakin die again. And wanting again to die with him." More tears came, and she looked away so that the others would not see them.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

The Jedi had tracked down where Nyax killed the first Yuuzhan Vong hunting party by following the lingering dark side energy they felt from the attack. Luke even compares the dark side energy he feels to what he felt back on Dagobah in the cave and it makes the hair on the back of his neck stand up:

By Luke's chrono, it had taken them four hours to find the first evidence of the thing or things they sought. They stood in the main manufacturing chamber of a furnishing concern and looked down at the dismembered bodies of Yuuzhan Vong warriors—and voxyn.

It was not evidence or deduction or luck that had led them here. Luke and the other Jedi could feel lingering dark-side energy imbued in the walls, the machines, the corpses. The sensation, so like what Luke had experienced within a certain cave on Dagobah, caused the hair on the back of his neck to rise.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Even in death, by using the power of the Force wellspring, Nyax is able to imbue his surroundings with his own hatred and causes tons of rubble to shoot out into the sky at Yuuzhan Vong ships and anything in the area:

The power-wielders who had hurt him were not visible. But two chunks of coral he could not feel with his own power, big ones, were approaching him from two different directions.

His enemies had to be aboard them, hidden by whatever power they possessed to block his senses. Since they never gave up, they must be coming back after him. They had to be aboard because he would not sleep until they were dead.

He roared out his pain and sent ton after ton of rubble into the sky.

—

Kell lost altitude and slid to a landing on a rooftop four kilometers from the ziggurat. From here, they would see the two Vong mataloks, cruiser analogs, approaching from north and south.

Two sprays of rubble leapt from the hole in the ziggurat, each going after one of the mataloks. Nyax's aim was getting worse; in the first few seconds of the attack, neither Vong ship took a hit.

And both fired, raining plasma projectiles as numerous as raindrops into the ziggurat.

Luke jerked as he felt his flesh burn. He looked at his arm, but no blackness appeared there, no seared flesh. It was Nyax, his pain being transmitted to all close enough to feel it, and he could see that pain reflected in the faces of Mara, Tahiri, Danni, even Kell.

Then the rubble streams hit the mataloks. They poured across the vessels, some small portions of them being swallowed by voids, the majority eating away at the yorik coral as though it were sugar. The mataloks sideslipped, desperately trying to avoid the streams of destruction, but the rubble blasts tracked them, followed them, wore them down.

A constriction in Luke's chest, one he had been unaware of until now, suddenly loosened, vanished. "He's dead."

"Lord Nyax?" Face frowned back at him. "I don't think so. Look, more rubble than ever is flying out of there."

"Luke is right," Mara said. Her voice had a distant quality as she tried to interpret what she felt through the Force. "Nyax is gone. But he's imbued his surroundings with some of his hatred. Some of his last intent."

The mataloks rose above the rubble-stream, launching a new volley of plasma before the blasts tracked them, tore into them again. In the distance, more Yuuzhan Vong capital ships raced toward the disturbance.

"It's going to continue," Luke said, "as long as some part of him is there. As long as some part of him can exert his will on his surroundings, and that wellspring of the Force allows it to happen. But he's gone." He took a deep breath. "Let's go home."

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Physicals/Augmentations

Nyax was subjected to growth hormones and cybernetic stimulation for years, which allowed him to grow to three meters tall:

"Human males don't grow to be three meters tall."

"They do if subjected to specific growth hormones and cybernetic stimulation for years starting in childhood or adolescence."

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Nyax had armor plates installed in his torso, head, elbows, and knees, and the medical droids that were supposed to tend to him believed he was intended to be a war machine of some sort:

"So who is this human male?"

"Unknown, sir. His identity was never provided to us, nor the nature of its armor modifications." Before Luke could ask, the droid hurried on, "It had hypoallergenic armor plates installed in its torso, head, elbows, and knees. The portions of its brain pertaining to human memory were largely replaced by computer apparatus. We of the maintenance staff concluded that it was to be a war machine of some sort, but beyond that we know nothing."

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Nyax was subjected to medical treatments that kept his bones growing long past the point they should have stopped which gave him more muscle mass. He also had a computer apparatus implanted in his brain when he was young that allowed him to learn to control the Force far out of proportion for someone his age:

"Except," Baljos interrupted, "he spent most of the intervening years in that suspended animation chamber, so he's physically younger than his chronological age. His vital processes were slowed. He was subjected to the medical treatments I mentioned earlier, treatments that kept his bones growing long past the point they should have sealed, that gave him lots more muscle mass. As a baby, he'd had a computer apparatus implanted in his brain by his mother; it helped give him enough focus—monomania may be a better word for it—to learn to control the Force far out of proportion to his age. When he was here, that apparatus was augmented to make his control even greater. It apparently stimulates what's left of his brain in ways beneficial to Force control."

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Nyax is described as a "hulking cyborg" outfitted with eight lightsabers jutting from his limbs:

Luke, Mara, and Tahiri confront Lord Nyax, a hulking cyborg humanoid fitted with an unbelievable eight lightsabers jutting from his limbs.

Source: The Essential Reader's Companion

Nyax was able to tear off a hatch and destroy four droids with nothing but his brute strength, since he was in a chamber with several ysalamiri which would have cut off his connection to the Force:

Baljos looked at the unit. The transparisteel cover had been thrown aside with such strength and violence that it was warped, the hinges along one side and locking latch on the other broken. The machinery that would have surrounded the sleeper like insulation was torn free from its housing and lay in pieces around the chamber. So did four medical droids—Luke thought it was four, gauging from the number of droid heads within sight, but he had to admit that their state of dismemberment made actual calculations difficult.

[...]

"Whatever it is," Face said. "The way I read it, this thing woke up, busted out, destroyed all the droids around it. With just its strength, you'll notice, because there are no burn marks on the droids in here or on the suspended animation unit. When it gets into other parts of the complex, it gets its hands on a lightsaber and finishes the job. Then it destroys the other droids and the ysalamiri."

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Nyax fights with a speed and savagery an experienced Yuuzhan Vong warrior had never seen before:

The pale thing fought with a savagery and speed unlike those of any warrior he had ever seen.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Nyax sends a Yuuzhan Vong warrior off his feet despite the warrior having blocked his attack:

The pale thing spun, sending its knee blade toward Denua Ku's guts. He blocked the sweep with his amphistaff, but the impact was tremendous; it threw him back off his feet. He rolled backward and came upright, saw one of his warriors perform a similar probing assault . . . and this warrior took a forearm blade through the throat.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Nyax drives Luke Skywalker back with his strikes and then folds a Yuuzhan Vong warrior through his armor:

"I know!" Luke shouted back. "It's working! I'm being delayed!" He stopped a forearm-swing and was driven back a step, stopped the follow-up elbow swing and was driven back a step, jumped back to avoid the knee-strike and discovered it was only a feint; Lord Nyax's leg snapped back and caught a Yuuzhan Vong warrior in the crotch, collapsing the warrior despite its armor.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Nyax has built-in failsafes that prevent him from stabbing himself with his own lightsabers:

Mara sighed. It had been a feint, an effort to trick the thing into spearing itself with its own weapons. But its designers had been too thorough. There were fail-safes.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Weakness

Nyax's one "weakness" is that he escaped from his chamber too early and wasn't able to have certain things downloaded into the components of his brain. He has his instincts, some combat training, and deep-level motivations to kill Jedi, enemies of the Empire, and to dominate areas strong in the Force, but he lacks memories, tactical skills, and even language:

"Does he have any weaknesses?" Mara asked.

"Oh, yes." Baljos gestured at the suspended animation unit. "He's not ripe."

"Ripe," Luke repeated. "It appears that a groundquake caused some ceiling rubble to drop onto one or more of the ysalamiri, killing them and damaging the unit. He woke up, burst out, went on a rampage, and fled. But he wasn't due to come out for another couple of years." Baljos pointed at one of the computer consoles. "All his operational programming was there, plus the refabricated 'Irek' memories Roganda planned to implant in him, and they weren't transferred over. He has his instincts, he has some combat programming, and he has some deep-level motivations—such as to seek out Jedi and kill them, to seek out hot-points of the Force and control them, to conquer the universe, little things like that. But he lacks memories, tactical skills . . . even language, I think. I doubt he's even verbal."

"So we can't even talk to him." Tahiri looked downcast. "Maybe that's a weakness, but it doesn't make things easier on us. He can't be reasoned with."

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Force Powers

Force Wellspring

This isn't a Force ability but a section I wanted to include for some context. Lord Nyax is drawn to the Force wellspring under the Jedi Temple of Coruscant/Yuuzan'tar and uses his Force powers to take control of a large construction droid in order to help him release it.

When the wall breaks and the wellspring is released/opened/revealed, its power is felt across the galaxy and we're shown the reactions from certain groups of Jedi. Jaina Solo, Kyp Durron, and Ganner Rhysode all flinched and jolted the ships they were flying from what they felt, and Valin Horn and the other Jedi trainees all experienced a powerful "nightmare" feeling with the surge being strong enough to jerk Valin awake off the couch he was laying on:

Above Borleias, on a routine surveillance sweep in her X-wing, Jaina Solo was jolted out of her detachment by a surge in the Force. She could feel Luke and Mara in the surge. She knew they were in danger. And she could see Kyp's X-wing wobble as he, too, was hit by the sensation.

Thousands of light-years away from Borleias, Ganner Rhysode, Jedi Knight, kept a firm hand on the controls of his rickety transport as he closed the last few meters to dock with the space station ahead. But his arms spasmed as the Force seemed to howl at him. His transport jerked forward, hitting the docking bay at a greater velocity than he intended. As he shook his head to clear it, he heard the dockmaster over his comlink: "Idiot."

In an artificial environment dome, part of an ever-growing station hidden away in the Maw, Valin Horn, Jedi apprentice, jerked awake so violently that he fell from his narrow couch. He sat up, trying to remember what nightmare had caused this reaction, but he couldn't. Then he heard the wailing of the infant Ben Skywalker from two compartments down, the voice of an adult trying to soothe him, the voices of other Jedi trainees as they compared details of what they'd just felt.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

When first exposed to the wellspring, Luke Skywalker can't even remember his own name, or that of his wife or Tahiri Veila. It takes him a few seconds to come to his senses and then when he wants to pull his lightsaber to his hand with a "casual display of the Force", the weapon flies to his hand harder than he intended and he has to drop it:

Luke swam out of a sea of—not pain, not shock, but something between exultation and complete confusion. His back was against a mound of rubble, and his wife and the girl were beside him. He couldn't remember their names, or his own.

Red fluid dripped down upon his shoulder. He craned his neck to look up and saw a body on the mound above him, that of a human man. Its right arm was missing and blood poured down the rubble below, one stream of it pooling and then dripping onto Luke.

Luke. That was it, Luke. And Mara and Tahiri. And the Yuuzhan Vong, and Nyax. Luke rose, saw his lightsaber a few meters away, and yanked it to him with a casual display of the Force. It struck his palm with far more energy than he'd intended, and he dropped it again.

[...]

Mara rose beside him. Luke had known she was unhurt.

"Force energy," she whispered.

This must have been a wellspring of it, he thought. The old Jedi Temple must have been built above because it was here. They were guarding it. And guarding the planet from it.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

It's described as a "wash of Force energy" and Luke can feel its power bolster him:

Luke reached up and found minds—dozens of them, all receptive to the Force. In the wash of Force energy emerging from the crack in the wall, he found he could reach any of them, all of them.

He projected a strong demand for silence, a sense of calm, and could feel them quiet. Then he formed a picture in his head: the building collapsing, the construction droid driving in reverse to get away. He projected that image with all the strength he could muster, bolstered by the Force wellspring.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Luke even calls it "pure power":

"That fountain of Force energy is what made Nyax stronger," Luke said. "It's pure power . . . and we can use it, too."

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Nyax draws on the Force wellspring to make himself stronger:

Without the ability to speak or recall his identity, Irek takes the name Lord Nyax from a Corellian myth, locates an abandoned Jedi temple, and taps into the Force wellspring there, increasing his power.

Source: Jedi Academy Training Manual

Nyax feels like he can reach down and "crack this world in two" thanks to the power of the Force wellspring and believes no other being has felt power like this before:

Power flowed through Nyax, such power as no being alive had ever felt. He could reach down into this world, reach through the false crust beneath him, through the natural stone crust beneath that, all the way to where stone turned to sluggish fluid and through to where superheated metals ran like river water. He could crack this world in two, could force the meaningless worker-things to convey him to another, and crack that one, too.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Telepathy/Mental Compulsion

Telepathy is the power to sense, communicate and manipulate the thoughts of others. Nyax is also very skilled at sending a mental compulsion at others and forcing them to do what he wants.

Nyax is proficient in the ability "Mind Trick" and has Force Power Mastery and Force Power Adept in Mind Trick as well:

— Jedi Academy Training Manual

Luke sees Nyax about a hundred meters away from him, and as he's looking at him through a pair of macrobinoculars, he feels Nyax as a "beacon of darkness" right before Nyax sends a mental compulsion at Luke. This makes him feel like two tons of duracrete had been dropped on him and then makes Luke want to walk across an imaginary walkway to reach Nyax, which would actually be Luke walking off of a ledge and killing himself. When Nyax walks away, Luke says he could breath again:

Across the avenue, at about the same altitude, someone stood in a viewport staring at him. At this distance, about a hundred meters, Luke could not be sure, but he thought it was a man. A very pale man.

[...]

Luke found he could sense the man in the Force—could do so without even reaching out for him. The man was a glowing light in the Force, a beacon in the midst of darkness. A beacon of darkness . . . but that suddenly didn't matter.

Luke felt his breath go out of him. It was as though the roof had slowly collapsed and deposited two tons of duracrete on his torso while he was distracted.

He glanced over at Face and Bhindi. They had the terminal running; the glow from its screen colored their faces blue. Bhindi removed a datacard from its slot in the terminal and made a noise of satisfaction. They were both utterly unaware of what Luke was seeing, feeling.

Luke knew that, when he turned his attention back to the distant viewport, the pale man would be gone; it was among the oldest tools in the bag of tricks of the makers of supernatural holodramas. But when he looked through the macrbinoculars again, the man was still there, motionless.

Luke unlatched the viewport's locks. All he had to do was step out on the walkway that now stretched between this building and the other. He could walk right up to this man and begin asking questions. But some faint stirring of alarm—his pilot's ability to glimpse and memorize topographical details—shook him out of the fog that had overcome his thinking.

There was no walkway before him. One step through this viewport and he'd plummet to his death.

The man's grin grew wider. Then he sidestepped and disappeared from sight.

Luke felt the great weight lift from him. He could breathe again. "Are you two done here?" he asked.

Face looked up, frowning. "Luke, are you alright?"

"No. Trouble's coming. Let's go."

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Although he admits he's probably just tired, Luke is afraid of the fact that Nyax could force such a powerful compulsion onto him and make him feel like a spice addict with no training:

"I know, I know. I need sleep. I'm tired." He stretched out on the cot. "Tired, and I have to admit it, scared of something that could sneak up on me and plant a Force-based suggestion in my mind. As though I were some spice addict with no resistance, no training."

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Nyax sends out a mental compulsion that forces several survivors on Coruscant to ignore their own safety and fight Yuuzhan Vong warriors, summoning them from all over the ruined undercity of Coruscant. The call brings them in droves but doesn't affect Face because he's still well nourished and hopeful while the "workers" living on Coruscant are starved and hopeless. However, Tahiri knows that Nyax could easily control Face if he put the effort into it and believes that he could even control her, Luke, and Mara Jade Skywalker:

Yuuzhan Vong warriors were scrambling over the rubble and rushing toward the construction droid.

Coruscant survivors rushed out of the construction droid's base to meet them. Unarmed, ill-fed, they still had a tremendous edge in numbers over the warriors, and Luke saw several of the Yuuzhan Vong go down under struggling masses of bodies. The stronger survivors picked up chunks of stone and brained the troops.

More Yuuzhan Vong entered. More survivors swarmed in, now coming from surrounding areas of rubble instead of just from the droid's base.

Luke looked back at the others. "He's near. He's calling to them. Calling for help."

Face pulled his helmet off, touched his forehead. He looked troubled. "I know. I can feel him. In my head. I want to go down there." He looked up into their worried expressions, offered them a wan smile. "Well, mostly I don't. But I can feel the draw."

"You're strong," Tahiri said. "Well fed. You have hope still. He'd have to exert himself more to control you. But I suspect he can. I'm not sure he can't control us."

[...]

Lord Nyax watched as his workers swarmed toward the warriors he could not sense. He did not like the fact that he could not feel them, but he did enjoy seeing his workers kill them—though it was usually at a cost of twenty or thirty workers per warrior.

But he was summoning more workers from all around. No matter how well they hid in the ruined undercity, his call reached them and forced many, most, to climb free of their hiding holes, to stumble and then walk and then race toward the scene of this conflict.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Nyax throws a piece of stone at Luke Skywalker, intending to hit the Jedi the moment he lands from a jump. He then leaps up and over Mara Jade Skywalker and Tahiri Veila as the two women jump down at him from above, and then Nyax launches a powerful mental attack against the three Jedi. The attack is strong enough to freeze the Jedi in their tracks and even cause Luke to collapse from the pain. However, once Tahiri powers through the pain Nyax is sending her, Luke and Mara are able to recollect themselves and defend properly:

Then he sensed something and looked up. A bar of energy flashed, and three people fell out of a hole in the ceiling.

They drifted laterally to the top of the slope of the black wall, riding it down, using their power to slow their descent, keep their balance, increasing the friction between the clothes on their feet and the wall's surface.

Lord Nyax moved to be beneath them. He ignited his blades, all of them. He knew they'd be here, knew it from the moment they stopped chasing him. He wished they'd go away instead of tiring him.

The foremost of them, the male, slid down until he was not far above Lord Nyax's reach, then leapt free, somersaulting to land somewhere behind him. Lord Nyax reached out as the male came down; he slid a sharp-edged piece of stone toward the male's landing area, timing it so that the stone would shear through the male's legs. But the male slowed his descent and rotation, landing atop the stone instead of in front of it, and bounded off, toward Lord Nyax. Meanwhile, the women leapt clear of the stone, spinning down toward him, igniting their weapons as they came.

Lord Nyax leapt free of the center of their formation, bounding up over the head of the red-haired female. He hit the stone wall feetfirst, shoved off, and rotated to a landing many steps away from the three pests.

Then he made a thought and drove it into their heads.

—

It hit Luke like a razorbug fired straight through his forehead. Luke staggered under the pain. His back hit the irregular floor. He waved his lightsaber up and in front of him, a defensive form, but there was no follow-up blow for him to counter.

There was, however, a new priority. He was to switch off his lightsaber and then go attack the Yuuzhan Vong. He leapt to his feet and turned his weapon off. He could see Mara and Tahiri doing the same.

But that would mean dying—and, worse, failing.

No, its what he had to do.

No, he couldn't do that.

He stood, frozen by the dilemma, straining against the thought that filled his mind, the thought that was slowly driving out every other consideration.

So he did what he had to whenever he was confused. He reached out, touching Mara in the Force. He didn't have to open his mind to her; his mind was as open as it could be, held open by Lord Nyax's thought. He just had to reach for her, and she was there, locked in as much confusion and pain as he.

She had no answer for him. He reached for Tahiri and found her to be identically immobile.

He felt Lord Nyax grow impatient, then angry, and Lord Nyax expressed his anger through pain. Luke felt his fingers and toes, hands and feet, shins and forearms explode. He fell, writhing, then stared in amazement as he realized that his limbs were still attached—the pain was real, but no injury had caused it. He could feel Mara's pain, feel Tahiri's.

There was something different about Tahiri's. He looked over to where she lay.

She was rolling to her stomach, forcing her way to her feet. Off-balance, weaving as she stood, she nevertheless managed to pick up her lightsaber and ignite it. She looked at Nyax, anger blazing in her eyes. "I know something about pain you don't," she said. "Pain drowns other people. I just swim in it." She took a step toward her tormentor.

Luke could feel Nyax's anger, his moment of confusion. And though Luke couldn't move, he could act. He reached out through the Force and grabbed the stone that Nyax had tried to use against him moments earlier. He jerked it toward his enemy.

And though he was weakened by pain, by distraction, it flew those few meters and slammed into Nyax's back, driving him forward, slamming him off his feet.

Tahiri leapt forward, bringing her lightsaber down in an all-out attack. Nyax managed to get one of his arm-blades up to intercept it, then kicked out, shoving off against a pile of rubble. He slid away from Tahiri, and the slide continued well past the point that it should, carrying him clear of her . . . but he left skin and blood behind on rubble he crossed.

Luke felt Nyax's astonishment, his outrage at having been wounded, however trivially. Then Nyax drove another thought into Luke's brain: Kill Tahiri.

This time, Luke was ready for it. He'd had a moment to center his thoughts and, most important, emotions. He was ready with his memories of Tahiri, all the time's he'd been delighted as she'd made another gain in her study of the Force, all the hopes he'd had for her future and happiness. He could hold up like a shield his memory of her love for his nephew Anakin Solo. All those memories blunted Nyax's attack, shattered its speartip.

Luke reached for Mara again and found her similarly armored, but with logic, not emotion. Running through her mind was a cold calculation of allies and opponents, actions and consequences. Uppermost in it was was a realization that Nyax could rule any individual, and out of individuals whole galaxies were made.

But deep beneath the analysis was a stream of emotion, an awareness of their son Ben, of what he would be if Nyax could find him and shape him.

Luke came up on shaky legs, felt Mara doing the same. And though Nyax was not letting up on the pain-energy, it affected Luke less now. He could feel Tahiri's part in that, the way she opened herself to the pain, was not daunted by it, was not shut down by it.

They faced Nyax as a single creature. The part of them that was Mara rejected the false truths Nyax tried to impose upon them. The part of them that was Luke rejected the false hatreds, the lying enmities. The part that was Tahiri made the pain part of what they were, a fuel for their strength.

Nyax looked between them, and a flicker of distress, a childlike expression of fear, crossed his features.

Then all four of them felt the wall break. Whatever was beyond it roared forth to sweep them away.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Nyax was using his mental compulsion to control construction droid workers in order to break free and release the Force wellspring underneath the Jedi Temple on Coruscant:

Luke could feel Tahiri's sense of shock; it matched his own. "Did he drive a hole all the way to the surface?" she asked.

"I think so," Luke said. He turned his attention to the beings at the summit of the construction droid. He could feel their confusion, too. Nyax, his objective accomplished, had released them. As their volition returned, their physical exertions, their outrage at the way they had been violated for so long, overwhelmed them.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Telekinesis

Telekinesis is a common Force ability that affords the user the ability to alter and distort the environment and reality around them.

Nyax is proficient with the ability "Move object":

— Jedi Academy Training Manual

Nyax lifts a piece of the floor with the Force to intercept an acid attack from a voxyn:

The voxyn, canny and old, charged to within three meters of Lord Nyax and then arched its back. It made a noise like a bedchamber's worth of carpet being suddenly ripped in two, and a gout of dark, smoking liquid sprayed from its mouth.

A portion of flooring between the voxyn and Lord Nyax tore free, lifting into the fluid's path. The voxyn's acid splashed across it, almost instantly burning through it, but its momentum was arrested. It and the flooring fell, the sound of the chemical reaction of the acid audible even at this distance.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Amped by the Force wellspring, Nyax easily uses the Force to shoot a "plug" some ten meters across in the ceiling up and out of sight and then divert all of the debris falling on him afterwards:

Nyax finished dancing. He turned to look at the Jedi. His expression was so full of uncomplicated happiness that it seemed implausible that he would every try to hurt them.

Nor did he attack them now. He simply raised a hand.

Above him, a portion of the ceiling, a plug some ten meters across, shot straight up and out of sight. Debris rained down, but drifted to one side before it could hit Nyax. Tremendous crashing noises emerged from the hole above, and the walls all around them began to shake.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Amped by the Force wellspring, Nyax floats up and through the hole he had in the ceiling and away from Luke Skywalker:

Luke thumbed his lightsaber into incandescence and marched toward the creature with Irek Ismaren's face. Let's finish this.

But Nyax, ignoring him, lifted straight up into the air and floated up through the hole his Force powers had made. In a moment he was out of sight.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Amped by the Force wellspring, Nyax twirls large boulders around himself while levitating in the air and creates a spray of rubble that launches debris strong and large enough to destroy coralskippers and as far as kilometers away:

Coralskippers rose from the formation in sudden flight, attempting to get away from the stream of crude projectiles, but those who rose first ran into another stream, this one moving much faster; chunks of rock and duracrete pounded into the yorik coral, eroding it like a super-powered sandblaster, destroying those vehicles.

At first glance Luke thought that Mara had initiated that attack, adding her strength to his and Tahiri's, but he realized after only a moment that it felt wrong. He leapt up through the hatch Mara had opened, landing beside her on the construction droid's roof. Tahiri was only a second behind him.

From here, they had a clearer view of the sky full of coralskippers and of the ziggurat behind them.

From the ziggurat emerged a column of rubble. As it rose, it parted, arcing away from its point of emergence in all directions like a water spray. But this spray was being flung kilometers in every direction, chewing through building tops and coralskippers as it landed.

And above its center, where the rubble no longer rose, floated Nyax. Giant boulders danced in and out through the rubble spray, weaving a lovely spiral through the air.

"Another Jedi academy graduate," Tahiri breathed. "He can lift really big rocks."

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Amped by the Force wellspring, Nyax would continue to launch several tons of rubble and divert streams of debris to take out flying coralskippers:

From here they could see the hole in the ziggurat roof widening. With every moment that passed, more tons of rubble poured up and out of the hole and flew out to pour onto surrounding kilometers of buildings. Some streams diverted to hose coralskippers out of the air. The lines of giant boulders still danced their merry circles around Nyax.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Amped by the Force wellspring, Nyax takes back control of a stream of debris that Luke Skywalker tried to hurl at him and sends it back at the Jedi Master:

As their vehicle came closer to Nyax, Luke stretched forth his hand. He snatched a portion of the rubble stream from beneath them, bent its course, sent it hurtling toward Nyax.

Nyax reacted without moving, regaining control of the stream, hurling it at Luke.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Force Sense

Force Sense is a basic power allowing Force sensitives to sense their surroundings, feel and determine the thoughts or feelings of others, feel ripples in the Force signifying important events, the presence of the dark side, or even sense the future.

Nyax knows the ability "Improved Sense Surroundings":

— Jedi Academy Training Manual

Nyax was able to sense Luke Skywalker and his team searching for him:

Lord Nyax felt the distant hunger. Something wanted him.

That was all right. He wanted it, too. Anything that was so anxious for him deserved to be encountered.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Luke Skywalker senses that Nyax senses him:

Luke could feel it as Nyax detected them. The pale giant rotated in the air to face them, his smile changing from one of simple pleasure to one of malice.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Hatred/Horror

Hatred is a dark side ability that allows a user to radiate their hatred in waves and send them at another person. Horror is a dark side ability that can raise the fear of another, potentially driving them to insanity.

Nyax quite possibly knows the dark side ability Hatred or Horror, and he is credited as knowing the talent "Channel Aggression":

— The Book of Sith: Secrets from the Dark Side

— Jedi Academy Training Manual

While fighting a Yuuzhan Vong hunting party, Nyax released such a powerful wave of dark side energy that human Senator Viqi Shesh was physically knocked over and stuck in a fetal position for the whole fight. She described the feeling as if she spent all of her years packing all of the hateful emotions a person could feel into a room and then having it burst at once and carrying her away.

She heard the voxyn's hisses go from excited to ferocious, heard their handlers call after them as they yanked leashes free from the handlers' grips.

"Jeedai!" called one of the warriors. "Now you die!"

Viqi heard the distinctive snap-hiss of a Jedi lightsaber igniting. One point on the far wall of the manufacturing chamber and the ceiling above it were illuminated by red light—moving light. The claws of the voxyn scrabbled as they charged for their prey.

Then there was another snap-hiss, and another, and another. The distant red glow brightened. Viqi saw the silhouette of a voxyn leaping high, vaulting intervening machinery, backlit by the glow—and then something rose to meet the voxyn in mid-flight.

It was not a Jedi, not a lightsaber blade. A block of machinery two meters on a side flew up from below and crashed into the leaping voxyn, striking with such force that Viqi heard the creature's bones shatter. The impact smashed the voxyn back through the air, a wobbly caricature of a once-living beast. The voxyn's body crashed onto the factory's duracrete floor and the block of machinery landed upon it, breaking more bones, and stuck there, not bouncing or rolling forward as it should have.

"Forward," Denua Ku said. He whipped his amphistaff free from his waist and charged after the other Yuuzhan Vong warriors, who now howled in rage and anticipation.

Viqi took two steps in Denua Ku's wake and then something crashed into her, took her from her feet, slapped her to the duracrete.

It was not a physical thing. It was despair and hatred, loathing and worthlessness, fear and howling rage. It was as though Viqi had spent every one of her years packing all the hateful emotions an ordinary person felt into a storeroom—and suddenly all the pressure had burst through the door and swept her away. She could only lie there, her arms and legs twitching outside her control, her stomach rebelling, her heart hammering inside her.

She heard the howl of the second voxyn, heard the ripping noise of the creature vomiting its acid at its prey. Then there was the sound of lightsabers swinging, hacking. Meat in great quantities slapping down onto the duracrete.

Viqi writhed in time with the war cries of the Yuuzhan Vong and, one by one, she heard them die under the almost musical tones of the lightsabers.

Then there was only the sound of lightsabers cutting, and cutting, and cutting.

The emotional agony that had gripped Viqi lessened—only a little. She managed to roll over onto her stomach and slowly, painfully came upright.

She knew the beings on the other side of the chamber had just killed everything that had entered the chamber with her. She wanted nothing more than to charge at them, to rip them to pieces with her bare hands.

But as she stood, some faint instinct of self-preservation rose within her, and one thought made up of words emerged: Run, or die.

She turned toward the doorway, and lurched out toward the light.

As she reached the doorway, she put her hand out to steady herself against the metal door that had once protected the factory's interior. It fell away from her grip, crashing down onto the duracrete with a tremendous clang.

The lightsabers in the distance switched off. Viqi froze. She waited, ears straining at the sudden silence.

Then she heard it, the padding of feet coming her way.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Elsewhere on Coruscant/Yuuzhan'tar, Luke Skywalker, Mara Jade Skywalker, Tahiri Veila, and even Danni Quee had all felt the powerful burst of energy Nyax released when fighting the Yuuzhan Vong hunting party. Luke felt "saturated" with a desire to kill every living thing in his vicinity, and Tahiri felt worse than after her torturing and conditioning from the Yuuzhan Vong and even admits that if the attack had been directed at her, it would have taken control of her:

Luke came awake and rose in a single smooth motion.

He didn't have to ask if Mara had felt it, too. She was awake, gripping her lightsaber, ready to ignite it.

Luke stepped out into the corridor. It was dimmed for sleeping, but Danni, too, was emerging, and Tahiri, who had been on guard in the corridor as the others slept, stared into one wall, through the wall, at something that was far away and toward the ground. "It's there again," she said, her voice faint.

Luke took a few deep breaths. He couldn't remember what he had just been dreaming—only that, for a moment, he had been filled, even saturated, with a desire to rise and kill every living being thing in his vicinity. Absurdly, he still felt loathing and contempt for his companions, for his wife, but as his mind and memory struggled to assert themselves, those emotions began to fade. "What did you feel?" he asked.

Tahiri shook her head, and Luke could finally see the lone tear flowing down her farther cheek. "Awfulness," she said. "More awful than when I was coming out of my conditioning and started to figure out what I'd almost become. It was all through me, through the Force. It almost had control of me. I think maybe it could have had control, if it had known I was here." The despair in her voice was heartbreaking.

None of the Wraiths had emerged from their new quarters. That made sense. This was a Force sending, a Force problem, and the Wraiths, largely oblivious to the Force, were not troubled.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Nyax causes two humans to fall to their knees, the woman of the two to gag:

There was a distant noise, a low-pitched roar that raised the hair on Viqi's arms and the nape of her neck. The man and woman hesitated, looking back the way Viqi had come.

Then it washed across her again, the feeling of hatred and lowness that had brought her down in the manufacturing chamber. It had the same effect on the man and woman; they paled and sank to their knees, the woman gagging, perhaps prevented from vomiting only by near-starvation.

Viqi scrambled around on the floor, turned toward her original direction of flight, and crawled as fast as paralysis gripping her arms and legs would let her.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Nyax's presence caused a group of people to riot, smashing everything in sight, and appeared to have been on stimulants for days or weeks:

Luke, Face, and Bhindi crouched in a crater that had been one corner of a skyscraper—the same skyscraper in which, minutes before, the pale man had stood. They were about twenty stories above the window the figure had occupied, and all three had macrobinoculars trained on the viewport Luke had, minutes before, tried to open.

The room beyond the viewport was filled with people. They wore tatters. Some wore nothing but dried mud and blood. There was a light in their eyes that suggested they were on stimulants and had been for days or weeks. They rampaged through the Starfighter Command office, destroying every piece of furniture, smashing every wall, a riot whose violence was directed at everything and nothing.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Nyax releases a wave of hatred that compels a group of workers to charge and attack twenty Yuuzhan Vong warriors:

Lord Nyax smiled as the warriors, twenty of them now, spread out in a semicircle. They approached him, amphistaffs ready, some of them handling thudbugs or razorbugs. They moved through the crowd of workers, contemptuously shoving those beings aside, hurling them off their feet.

The beam Mara was on bobbed more deeply as Luke arrived. He stretched out behind her and pulled out his own macrobinoculars.

Mara felt a sudden surge of hatred—not for Luke, not for Lord Nyax, but for the Yuuzhan Vong. She knew it to be a sentiment from outside her, and that kept it from being quite as compelling as it could have been.

And in that same instant, the workers screamed in rage of their own and swarmed the Yuuzhan Vong warriors.

The warriors swung and stabbed. Mara saw workers pierced through heart and gut and brain. When those attacks were not instantly mortal, they continued running and leaping at the Yuuzhan Vong, crashing into them, bearing them to the floor by weight of numbers.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Even in death, by using the power of the Force wellspring, Nyax is able to transmit his pain to anything close enough to feel it. Luke Skywalker feels as if his skin was burning and saw that the pain was affecting Mara Jade Skywalker, Tahiri Veila, Danni Quee, and even the non-Force sensitive Kell:

The power-wielders who had hurt him were not visible. But two chunks of coral he could not feel with his own power, big ones, were approaching him from two different directions.

His enemies had to be aboard them, hidden by whatever power they possessed to block his senses. Since they never gave up, they must be coming back after him. They had to be aboard because he would not sleep until they were dead.

He roared out his pain and sent ton after ton of rubble into the sky.

—

Kell lost altitude and slid to a landing on a rooftop four kilometers from the ziggurat. From here, they would see the two Vong mataloks, cruiser analogs, approaching from north and south.

Two sprays of rubble leapt from the hole in the ziggurat, each going after one of the mataloks. Nyax's aim was getting worse; in the first few seconds of the attack, neither Vong ship took a hit.

And both fired, raining plasma projectiles as numerous as raindrops into the ziggurat.

Luke jerked as he felt his flesh burn. He looked at his arm, but no blackness appeared there, no seared flesh. It was Nyax, his pain being transmitted to all close enough to feel it, and he could see that pain reflected in the faces of Mara, Tahiri, Danni, even Kell.

Then the rubble streams hit the mataloks. They poured across the vessels, some small portions of them being swallowed by voids, the majority eating away at the yorik coral as though it were sugar. The mataloks sideslipped, desperately trying to avoid the streams of destruction, but the rubble blasts tracked them, followed them, wore them down.

A constriction in Luke's chest, one he had been unaware of until now, suddenly loosened, vanished. "He's dead."

"Lord Nyax?" Face frowned back at him. "I don't think so. Look, more rubble than ever is flying out of there."

"Luke is right," Mara said. Her voice had a distant quality as she tried to interpret what she felt through the Force. "Nyax is gone. But he's imbued his surroundings with some of his hatred. Some of his last intent."

The mataloks rose above the rubble-stream, launching a new volley of plasma before the blasts tracked them, tore into them again. In the distance, more Yuuzhan Vong capital ships raced toward the disturbance.

"It's going to continue," Luke said, "as long as some part of him is there. As long as some part of him can exert his will on his surroundings, and that wellspring of the Force allows it to happen. But he's gone." He took a deep breath. "Let's go home."

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Force Jump

Force Jump or Leap is the usage of the Force to augment one's jumping ability.

Nyax is proficient in the ability Force Jump, called "Surge" here:

— Jedi Academy Training Manual

Nyax jumps up a half dozen meters:

Lord Nyax leapt upward a half-dozen meters and then, impossibly, just hung there in space, smiling down at the Jedi and the Yuuzhan Vong.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Nyax retreats from Luke, Mara, and Tahiri, sometimes jumping from building to building in leaps greater than what the Jedi could do:

Lord Nyax led the three Jedi on a high-speed run through the ruins of Coruscant. He could travel faster than they could, because from time to time he'd simply leap from one building to the next one over, usually a leap too great for them to match.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Crucitorn

Crucitorn is a Force ability that allows a user to decrease physical pain or transcend it beyond their normal thresholds.

Amped by the Force wellspring, Nyax uses the Force to overcome the pain of being struck by two thudbugs/razorbugs and then to try and force feeling and sensation back into his legs:

Something slammed into his back, just below the point where his internal armor plate protected him. His eyes snapped wide. He had not felt it coming. He used his power to overcome the pain.

A second thing struck him. He felt bones in his lower back shatter. Numbness flowed across his legs. He extended greater control over himself, desperately trying to force sensation into those limbs, as he turned.

His third antagonist, the smaller female with the yellow hair, rode another boulder, lying upon it and gripping it with one hand. She looked at him with alien mercilessness in her eyes. She barely registered in his special senses—she must have closed herself off to the power, reducing his ability to detect her, his ability to anticipate her moves.

Something was wrong. He had the pain under control. He was full of the power. He should be able to make anything happen, anytime.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Lightsaber and Combat Skill

Nyax is proficient with lightsabers, pistols, and simple weapons:

— Jedi Academy Training Manual

Nyax has had almost all of humanity burned out of his brain and is a predator whose only goal is to dominate:

"I guess that leaves me with only one more question." Luke returned the datapad to his belt pouch and prepared himself for what he expected to be more bad news. "Is there any way to save him? To befriend him, teach him about the light side?"

Baljos finally became serious. "I don't think so. He's had almost all humanity burned out of his brain. He's just a predator whose only goal is to dominate."

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Nyax fights and defeats a Yuuzhan Vong hunting party and two diseased voxyn. He starts the fight off by killing a voxyn by smashing its body with a large piece of machinery and then cuts the remaining warriors and voxyn to pieces:

She heard the voxyn's hisses go from excited to ferocious, heard their handlers call after them as they yanked leashes free from the handlers' grips.

"Jeedai!" called one of the warriors. "Now you die!"

Viqi heard the distinctive snap-hiss of a Jedi lightsaber igniting. One point on the far wall of the manufacturing chamber and the ceiling above it were illuminated by red light—moving light. The claws of the voxyn scrabbled as they charged for their prey.

Then there was another snap-hiss, and another, and another. The distant red glow brightened. Viqi saw the silhouette of a voxyn leaping high, vaulting intervening machinery, backlit by the glow—and then something rose to meet the voxyn in mid-flight.

It was not a Jedi, not a lightsaber blade. A block of machinery two meters on a side flew up from below and crashed into the leaping voxyn, striking with such force that Viqi heard the creature's bones shatter. The impact smashed the voxyn back through the air, a wobbly caricature of a once-living beast. The voxyn's body crashed onto the factory's duracrete floor and the block of machinery landed upon it, breaking more bones, and stuck there, not bouncing or rolling forward as it should have.

"Forward," Denua Ku said. He whipped his amphistaff free from his waist and charged after the other Yuuzhan Vong warriors, who now howled in rage and anticipation.

Viqi took two steps in Denua Ku's wake and then something crashed into her, took her from her feet, slapped her to the duracrete.

It was not a physical thing. It was despair and hatred, loathing and worthlessness, fear and howling rage. It was as though Viqi had spent every one of her years packing all the hateful emotions an ordinary person felt into a storeroom—and suddenly all the pressure had burst through the door and swept her away. She could only lie there, her arms and legs twitching outside her control, her stomach rebelling, her heart hammering inside her.

She heard the howl of the second voxyn, heard the ripping noise of the creature vomiting its acid at its prey. Then there was the sound of lightsabers swinging, hacking. Meat in great quantities slapping down onto the duracrete.

Viqi writhed in time with the war cries of the Yuuzhan Vong and, one by one, she heard them die under the almost musical tones of the lightsabers.

Then there was only the sound of lightsabers cutting, and cutting, and cutting.

The emotional agony that had gripped Viqi lessened—only a little. She managed to roll over onto her stomach and slowly, painfully came upright.

She knew the beings on the other side of the chamber had just killed everything that had entered the chamber with her. She wanted nothing more than to charge at them, to rip them to pieces with her bare hands.

But as she stood, some faint instinct of self-preservation rose within her, and one thought made up of words emerged: Run, or die.

She turned toward the doorway, and lurched out toward the light.

As she reached the doorway, she put her hand out to steady herself against the metal door that had once protected the factory's interior. It fell away from her grip, crashing down onto the duracrete with a tremendous clang.

The lightsabers in the distance switched off. Viqi froze. She waited, ears straining at the sudden silence.

Then she heard it, the padding of feet coming her way.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Luke Skywalker even suggests that he, Mara, and Tahiri help Yuuzhan Vong warriors fend off the crazed workers because they "desperately" need any resource they can get to help with dealing with Nyax:

"We have to help," Luke said.

Mara turned. Luke was wrapping the cord of his belt-grapnel, long abandoned but definitely a useful tool for the exploration of Coruscant's lower reaches, around the metal beam.

"Help who?"

"Help the Vong. Yeah, I know, I know, it's something you've never heard anyone say before." Luke rolled off the beam and fell, his descent arrested by his hand on the cord; more cord deployed from his belt as he descended. "I'm not worried about the fate of the Yuuzhan Vong," he told her. "But we desperately need any resources we can use against Lord Nyax."

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Nyax easily kills a sickly voxyn:

In the corner of her eye, she saw the voxyn charge Lord Nyax. He dodged under the beast's leap and flexed an arm. His elbow-blade sheared through the voxyn's gut, slicing the beast cleanly in two. It landed in pieces behind him.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

Nyax fights a large group of Yuuzhan Vong warriors and the Jedi Luke Skywalker, Mara Jade Skywalker, and Tahiri Veila. He kills eight Yuuzhan Vong warriors in the first eight seconds of the fight and even very nearly manages to get Luke and Mara to attack each other with the power of his hatred:

Viqi watched the huge pale man slaughter Yuuzhan Vong warriors.

The first two warriors stopped a dozen steps from the thing and hurled thudbugs. The pale man twitched and the lightsaber blades from one forearm and one knee rose, incinerating the living weapons.

Two more warriors raced up and, under cover of more thrown thudbugs, charged, whipping their amphistaffs around, one lashing out with the tail and the other with fangs.

The pale man stepped in close to the second warrior. The first warrior's fang attack missed by a meter. The pale man's left forearm blade lashed out at the second warrior, who blocked the attack by catching the blade in an amphistaff coil. Then the pale man's left elbow blade raked across the warrior's throat, separating it from his body. Meanwhile, the pale man's right-arm, right-elbow, right-knee blades rose, darted, swayed, and wherever they went, incandescences flared—sign of thudbugs being vaporized.

The pale man flipped the dead warrior's amphistaff toward the first warrior. The warrior contemptuously swept it out of the way, overcorrected as his own staff came back to block a lightsaber thrust—and could not block the other lightsaber blade as it simultaneously thrust into his helmet's eye socket. He fell, smoke pouring from the mask as he died.

More warriors arrived—two still threw thudbugs, four more skidded to a stop beside them and waited for a bare second to calculate their strategy.

A piece of ceiling steel whirled down like a spinning sawblade from above. It flashed across the warriors' position at knee height, and just for a fraction of a second Viqi thought that it had missed. Then those six warriors collapsed, legs severed at the knees, blood gouting from the stumps and limbs.

Seconds had passed. Eight Yuuzhan Vong warriors and their voxyn were dead. Seventeen more remained.

These warriors approached more cautiously. Directed by Denua Ku, they circled around the smiling, confident pale man who towered over them.

The whirling steel panel came around for another pass, but this time, a chunk of machinery, an air-cooling unit a meter on a side, fired off from the floor as though it were a guided missile and hurtled into the sheet's path. The sheet wrapped around it with a ferocious, almost feral shriek of metal bending, and both fell to the floor.

The pale man looked off to Viqi's left. She followed its gaze. There, advancing on the pale man, lightsabers lit, were Luke Skywalker and Mara Jade.

—

Luke and Mara approached Lord Nyax and his Yuuzhan Vong attackers. They kept their guards up, their senses—both physical and Force—alert.

Luke searched the face in front of him. He looked for some trace of humanity. He saw only smiling mockery, and he could feel the thing through the Force, its appreciation at having slaughtered warriors, its appreciation at the thought of slaughtering Luke and Mara.

There was no recognition in its emotion, no acknowledgement of kinship of any sort.

"I don't know if you can understand me," Luke said. "But whatever you're doing, whatever your plans are, I have to stop you."

Lord Nyax's smile grew broader. It seemed to recognize Luke's intent, even if it could not grasp his words.

Then it answered—not in words, but in images. Luke saw the power of its will, expressed through the Force, rolling over the remaining people of Coruscant like water roaring down a canyon through a burst dam. He saw them sweeping across Coruscant, killing and eating everything in their way—the Yuuzhan Vong, the disobedient, the Force-blind. He saw the workers here boarding the machine beneath their feet, crashing it through kilometers of buildings until they came to some place, a source for more power to fuel this glorious, deliriously happy destructive impulse.

In that instant, Luke joined in the plan. He longed to slaughter the outsiders, those who did not understand or join. He longed to taste their flesh.

He turned to Mara, beckoning her to join. She was facing the Yuuzhan Vong warriors, preventing them from surprising Luke with an attack, but her gaze was yanked to Luke. Her eyes widened, and he could feel her leaning toward him, leaning toward acceptance of this crucial duty.

But the sight of her brought memories. Luke saw worlds of beauty. He saw his son, composed of Luke and Mara and years to come. Around the edges of Lord Nyax's command he felt the Force, its other natures, the life from which it flowed.

He turned back toward Lord Nyax and struggled to find the words to express his thought. "I . . . stand . . . in . . . your . . . way."

It was the Jedi way. Jedi did not attack. But to position oneself in the path of a violent aggressor who would not yield achieved the same result.

[...]

And here he was again. "I stand in your way," Luke repeated, and was pleased that he had regained control over his voice. "What you see, you will not achieve."

The expression on Lord Nyax's face turned from mocking amusement to seriousness . . . even sadness, for a brief moment, as though the thing at last recognized kinship and discovered that it did not bridge the gulf between the two of them.

Then it charged.

—

Kell finished binding Viqi's hands behind her back and looked up in time to see Lord Nyax lunge toward Luke.

Luke raised his lightsaber, caught the downward sweep of Lord Nyax's right-hand forearm weapon. He spun clockwise, narrowing his profile as the left-hand forearm blade thrust toward him, and kept his guard up in time to intercept the right-hand elbow blade. Mara leapt forward, unleashing two fast blows that the thing's left-elbow blade caught, then folded over nearly double as she leapt back from a strike from its left knee.

The Yuuzhan Vong warriors unloaded handfuls of thudbugs and razorbugs, heedless of which of the targets they might hit, but the two Jedi and Lord Nyax flicked the weapons out of the air or dodged them entirely.

Two Jedi? Three. Suddenly Tahiri was in their midst, coming up on Luke's left, blocking a follow-up blow from the elbow blade on that side.

[...]

Denua Ku watched the pale Jeedai, and for a moment admiration almost drowned out the revulsion he felt at the notion of having abomination-machines like lightsabers touching one's own flesh.

The pale thing fought with a savagery and speed unlike those of any warrior he had ever seen. And it was untrained. With his experienced warrior's eye, he could see that its movements were instinctive, a fact revealed in the creature's failure to throw effective combinations of blows, its inability to gauge which way its enemies would leap when it attacked them.

If it had been born Yuuzhan Vong, if he'd been able to train it for a year, even half a year, he could have turned this thing into the greatest warrior who was not himself named a god. As it was, he'd have to kill this thing.

Even if the Jeedai, too, wanted it dead, it was still an abomination. And it was the greater threat. It had to die first. He threw his last razorbug, then lunged forward into hand-to-hand range, probing at the pale thing's back with the tail-tip of his amphistaff.

The pale thing spun, sending its knee blade toward Denua Ku's guts. He blocked the sweep with his amphistaff, but the impact was tremendous; it threw him back off his feet. He rolled backward and came upright, saw one of his warriors perform a similar probing assault . . . and this warrior took a forearm blade through the throat.

Nine Yuuzhan Vong warriors down. Sixteen to go. The numbers were becoming worse.

A tremendous mechanical roar shook the chamber. It lowered slightly in volume but became steady, filling the air.

—

"It's a delaying tactic!" Mara shouted over the roar.

"I know!" Luke shouted back. "It's working! I'm being delayed!" He stopped a forearm-swing and was driven back a step, stopped the follow-up elbow swing and was driven back a step, jumped back to avoid the knee-strike and discovered it was only a feint; Lord Nyax's leg snapped back and caught a Yuuzhan Vong warrior in the crotch, collapsing the warrior despite its armor.

Every step took the Jedi and the warriors toward the center of the chamber. The floor vibrated beneath their feet.

"What?" Mara said.

"I didn't say anything!"

"Not you! Speak up, Face!"

Luke waved Mara back. She jumped up and backward in a somersault, taking her out of Lord Nyax's range, and took out her comlink, holding it up to her ear. Tahiri took her place, swinging her lightsaber defensively, eyes wide as she analyzed her attacker's motions and patterns.

[...]

Unable to hear, Mara bit off a curse. She tucked her comlink away and jumped back into the fight, deflected a pair of thudbugs, took a swipe at Lord Nyax's hand; its arm rotated and it caught the attack on its lightsaber blade.

Luke flipped over the pale thing, striking as he went; his blow was blocked.

Tahiri, in front, lunged forward . . . and stumbled, right into the path of a knee blade. Mara reached out, an effort to shove with the Force, knowing that she was too late, knowing that the knee-blade would emerge in a fraction of a second from the back of Tahiri's skull—but Tahiri whipped to the side, still in control, still in balance, even as Luke crashed feetfirst into Lord Nyax's neck, forcing its head down toward its own knee-blade.

The blade turned itself off. Lord Nyax's head passed through empty space. Luke, backflipping to his feet, offered up an expression of bafflement and frustration.

Mara sighed. It had been a feint, an effort to trick the thing into spearing itself with its own weapons. But its designers had been too thorough. There were fail-safes.

The floor rocked under their feet. Mara felt the crash from below as much as she heard it.

Lord Nyax leapt upward a half-dozen meters and then, impossibly, just hung there in space, smiling down at the Jedi and the Yuuzhan Vong.

Mara realized, a fraction of a second too late, that it had merely grabbed the same cord by which she and Luke had descended. Then the floor went out from under her.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

NOTE: The fight ends here because Nyax activated a machine that put a hole in the floor, separating him from the Yuuzhan Vong and Jedi.

After all this, a fight with Nyax was something Luke Skywalker wasn't even sure he himself could win:

"We're going down there." Luke closed his eyes, just for a moment, as the weight of that decision pressed upon him. He was about to lead his wife and a teenager into a situation he wasn't sure he could handle, a situation that was likely to get them all killed.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

The strategy that enabled the three Jedi to defeat Nyax was based on Tahiri using her Yuuzhan Vong half's skills to basically become invisible in the Force. While Luke and Mara Jade were distracting Nyax with frontal attacks via the Force and their lightsabers, Tahiri snuck around the back and hit Nyax with two thudbugs/razorbugs. The pain from these attacks made Nyax lose control of the debris he was swirling around and eventually fall to his death:

Luke could feel it as Nyax detected them. The pale giant rotated in the air to face them, his smile changing from one of simple pleasure to one of malice. "This is going to be bad," Luke said.

Mara nodded. The wind at this altitude whipped her hair into a life of its own, making it look like a candle flame in a strong breeze. "Any ideas?"

"I have one." Tahiri knelt to improve her balance while she stared ahead. In the distance, this stream of boulders took a sharp turn, then moved to within a few meters of Nyax's position and beyond. "Just past that point. Distract him. I'll finish him."

Luke cocked an eyebrow at her. "You'll finish him. How?"

There was something in Tahiri's eyes that sent a chill down Luke's spine. "He could fight the Jedi just by feeling us in the Force," she said. "He couldn't feel the Yuuzhan Vong, so he had to watch. Well, I'm both." She rose and turned away from Luke and Mara, then took the long leap to the next flying boulder back in line. She raced its length, then leaped again to the third boulder down.

"What do you say we take her at her word?" Mara said.

"I'm too tired to argue."

Their boulder reached the end of its straightaway course and turned. It turned more violently than its predecessors had, but Luke and Mara could feel Nyax's intentions in the Force; they kept their feet planted and did not budge.

As their vehicle came closer to Nyax, Luke stretched forth his hand. He snatched a portion of the rubble stream from beneath them, bent its course, sent it hurtling toward Nyax.

Nyax reacted without moving, regaining control of the stream, hurling it at Luke.

Luke leaned over backward, rotating his boulder with him. The oncoming stones crashed into its side and bottom as the rotation continued.

Upside down, clinging by virtue of her enhanced Force strength, Mara ignited her lightsaber and hurled it. It twirled under the flow of boulders, almost invisible through the dense rain of duracrete; then, as it came within meters of Nyax, it twirled up and at him.

His expression changed to one of startlement. With none of his own blades active to protect him, he slipped sideways, out of the lightsaber's path, then turned to watch it as Mara directed its flight. She sent it around in a long loop, preparing it for another approach.

Mara and Luke came upright as their boulder completed its rotation, and Luke could feel Nyax's attention on him, too, waiting for his attack. Luke made it, shoving in the Force, trying to hurl Nyax off balance and onto Mara's blade. The attack was a success, but Nyax activated all his blades as he shoved, and with contemptuous ease he swatted Mara's lightsaber away.

—

Power flowed through Nyax, such power as no being alive had ever felt. He could reach down into this world, reach through the false crust beneath him, through the natural stone crust beneath that, all the way to where stone turned to sluggish fluid and through to where superheated metals ran like river water. He could crack this world in two, could force the meaningless worker-things to convey him to another, and crack that one, too.

And he was tired of these creatures. They were weaker than he, but so stubborn. Even inventive.

Nyax raised his hands. He would crack the stone they rode on and send it and them hurtling down into the ruins.

Something slammed into his back, just below the point where his internal armor plate protected him. His eyes snapped wide. He had not felt it coming. He used his power to overcome the pain.

A second thing struck him. He felt bones in his lower back shatter. Numbness flowed across his legs. He extended greater control over himself, desperately trying to force sensation into those limbs, as he turned.

His third antagonist, the smaller female with the yellow hair, rode another boulder, lying upon it and gripping it with one hand. She looked at him with alien mercilessness in her eyes. She barely registered in his special senses—she must have closed herself off to the power, reducing his ability to detect her, his ability to anticipate her moves.

Something was wrong. He had the pain under control. He was full of the power. He should be able to make anything happen, anytime.

He did not understand, for he had not been trained in the ways and use of the Force, that the catastrophic failure of the body's functions could interfere with use of the Force. All he did understand was that his control over the boulders, over the debris flow from the ever-widening hole beneath him, was faltering.

The yellow-haired female held up a third missile. It had legs that writhed as she held it.

Nyax gaped at her. It was one of the alien creatures, one of the types flung by the warriors he could not feel. Her type was not supposed to use this. Only the flat-nosed aliens were.

It was unfair. She had cheated.

Before she could throw it, Nyax lost control. He fell, screaming, into the pit he had created.

Source: The New Jedi Order - Enemy Lines II: Rebel Stand

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