Lyrl Dox is the genius son of Vril Dox and Stealth. Still a child, he took control of his father's team L.E.G.I.O.N. However, Vril eventually outmaneuvered his son by injecting him with a serum to limit his intelligence. Vril would go on to say that he had killed his son, later proven to be a lie.
We discover Lyrl again in a jungle as a older teen in R.E.B.E.L.S. He is hunted down on the planet Voorl. It is revealed that his mother Stealth died defending him from rogue L.E.G.I.O.N robots. Lyrl is resentful toward his father for leaving them in the jungle of planet Voorl to return to serving as the leader of L.E.G.I.O.N when he's found, and originally thinks that his father is behind the murder of his mother. Shortly after being found, Starro's forces, who are in control of L.E.G.I.O.N and were behind the murder of Stealth, Lyrl's mother. Brainiac 2 tells his team that L.E.G.I.O.N. killed Stealth while originally trying to get to Lyrl.
Starro takes control of Lyrl and restores his 12th-level intellect that his father took from him in order for him to live a normal childhood and sense of morality. After regaining his intellect, he insists on being called Brainiac 3. With Lyrl under Starro's control, Lyrl begins devising a way to remove the blockade that his father put up around the quadrant that Starro was inhabiting, effectively stopping him from expanding his conquest.
Lyrl encounters his mother, who is a Black Lantern, and father again on Voorl after making a transmatter portal that can reach any place in space while escaping two of Starro's former generals turned Black Lanterns. Together they try to find a way to take down the Black Lanterns. At the time, Vril Dox was part of the Sinestro Corps having been inducted moments before when a Sinestro Corpsman died in his proximity and they'd attained knowledge from Captain Comet that by hitting a Black Lantern with two different colors you can kill them. So the two Brainiacs try to devise a way to emulate a power ring's light using Adam Strange's weaponry. Though they successfully emulated a Green Lantern's light, they were stopped before they could hit any of the Black Lanterns. Out of anger, Vril uses his yellow power ring to sweep all of the Black Lanterns and Starro's forces back through the portal Brainiac 3 made. When Lyrl tells his father that he can't just dump all of the Black Lantern's on his master, Starro, Vril throws his son in, as well, believing him lost to Starro's control.
Starro and his forces fight the Black Lanterns, including Lyrl, for three days. It was with the transmatter portal that they eventually disposed the Black Lanterns into the event horizon of a black hole. During the fighting, Lyrl noticed that his master would grow more excited as he realized he could not kill the Black Lanterns, it was due to this that he deduced that what his master truly wanted was to die. Wanting nothing but to please Starro, he opens a transmatter portal to Vril Dox's location and snatches him in the middle of a meeting between himself and his R.E.B.E.L.S. team. While Vril tries to overpower his son, Lyrl quickly makes a fool out of him in a hand-to-hand confrontation, revealing that he taught himself all twenty-seven levels of Lythlylian Grappling and after getting him in an armbar and getting his attention, he revealed that Starro will step through a transmat portal and will wind up in his father's lap instead of where he intended him to go and tells his father he expects he has concocted some sort of device to defeat Starro before allowing him to leave.
Brainiac 3 is later seen after the defeat of Starro with Pulsar Stargrave, a being he refers to as a Solaris Class Macroprocessor created when imploding a neutron star. Pulsar Stargrave refers to Brainiac 3 as father, and together they launch an attack Colu in an attempt to take it over. His father, Vril Dox II, was returning his father Brainiac, who he had recently captured, to Colu at the time and after doing some PR was in Brainiac's cell when his son's awoke Brainiac from his thought-cell. With his father awakened, Vril took flight, attempting to contact his smarter son who was trying to get the Coluan council to surrender control of the data-core of Colu to him. Little did he know that Brainiac was already taking control of the data-core.
Brainiac 2 tells his son to use thermonuclear weaponry, but Brainiac reveals that he already thought of it before them and launches a number of missiles at his son and the council. The council is killed in the explosion, but Brainiac 2 survives due to his force field and Brainiac 3 aids by sucking away the radiation. Brainiac 2 asks why and Brainiac 3 tells him that he has no intent on facing Brainiac alone and asks if he has a plan. Brainiac 2 tells him that he's going to retreat and get a secret weapon, leaving his son to fight Brainiac alone. Brainiac ensnares Pulsar Stargrave in a field that feeds off of Pulsar Stargrave's energy, the field only strengthens when hit by Stargrave's energy and thus is effectively impenetrable.
While Brainiac 2 was gone, Brainiac 3 lost control of Pulsar Stargrave. When Brainiac 2 returns for Brainiac 3, Lyrl angrily lashes out and points a gun at his father for leaving him to die. Brainiac 2 insists that he left to get his secret weapon, which was Lobo, who engages Pulsar Stargrave. The two try to engage Brainiac in the data-core of the planet, but these are revealed to be holograms while they tried to steal control of the data-core. This proves impossible after Brainiac uncovers their ruse and tracks their neural interface, disabling their minds. While downloading their minds, Brainiac is emotionally moved by the contents of his "son's" mind, which was the plan when Brainiac 2 unsealed those emotions for Brainiac to uncover. Shaken and defeated by the emotions Brainiac 2 felt, wanting his father's approval and hating himself for never receiving it, Brainiac is forced to flee, but takes Pulsar Stargrave and the Coluan data-core with him in doing so.
For his help, Brainiac 2 sets out to clear Brainiac 3's name. Currently, Vril uses his son as a secret weapon with his higher-level intellect. He had his son design a bomb that would destroy a neighboring sun in an attempt to discredit two rookie Green Lanterns who managed to dispose of the bomb.
Powers and Abilities
Brainiac 3 is a 12th level intellect which surpasses his father, Brainiac 2's, 10th level intelligence, but slightly under his grandfather, Brainiac's Nth level intelligence. A 12th level is almost unheard of, even on Colu, where they're known for their intelligence. Brainiac 3's intelligence, in comparison to Brainiac's, should be thousands of times more powerful than the average human. Lyrl, even as an infant, showed enough intelligence to successfully take reins over his father's L.E.G.I.O.N. He has shown to excel in technological fields, being able to calibrate weaponry to mimic Green Lantern light and building a transmatter portal that can reach anywhere in space. The upper-limits of what his mind can do is currently unknown.