The Maha Yogi is actually an immortal that has had different identities for numerous centuries. He was born c. 8250 BC, at the closing years of the Hyborian Age. He was born in Vanaheim and probably is the last surviving member of the ancient Vanir. Granted psychic powers by the Caretakers of Arcturus, he managed to survive for centuries after discovering a fragment of a mystical gemstone called the Hellfire Helix.
According to "Incredible Hulk" vol . 2 #210 (April, 1977), the immortal Maha Yogi was present at the building of the pyramids. He was there when Julius Caesar was assassinated (44 BC).
The Maha Yogi was created by Stan Lee and Jack Kirby and first appeared in Journey Into Mystery #96.
Many centuries ago, he posed as Merlin the Magician. He had trouble facing the invading Kang the Conqueror (Strange Tales #134- July, 1965). His attempt to recruit Modred the Mystic as an apprentice led the boy right at the hands of Chthon. The false Merlin was eventually exposed as a fraud by the real Merlin. The real Merlin defeated the imposter and placed him into a special crypt where he stayed in suspended animation.
Major Story Arcs
One day he would awake in our world and battle Thor. The Thunder God tricked him into returning to his crypt in a New York museum where he slept for another millennium. He would later awake and alter his appearance to become the Warlock. He would capture members of the X-Men including Professor X and take them to his subterranean cavern where his headquarters was an actual medieveal castle. He revealed to them an apparatus he invented that was powered by his brain. It was suppose to turn the minds of normal mortals backwards- to the level of mankind at the time of King Arthur. They would no longer have the scientific weapons or skills to oppose the forces of the Warlock. However the Warlock's plan for world domination is thwarted by the X-Men and returns to a comatose state.
Sometime later, the Warlock appears in New York as the Maha Yogi and performs numerous shows where he ends up hypnotizing the audience to make them his psychic servants. His plan was to tour city to city and create a mass, psychic army. Two members of the X-Men, Hank McCoy and Bobby Drake attend one of his shows and realize that the Maha Yogi is an old enemy. Iceman and the Beast confront the Maha Yogi backstage where they manage to defeat him by using deafening sound blasts from a hi-fi tape console to disorient him. The Maha Yogi surrenders and his plan to enslave millions is thwarted by the two mutants.
The Maha Yogi went into hiding after his defeat at the hands of the X-Men and began to build his little empire. He had numerous trained mercenaries as his servants and also acquired a monstrous bodyguard called Mongu. Dr. Druid discovered that the Maha Yogi had gained total control of his fragment of the Hellfire Helix which he calls the Jewel of Jeopardy and sets a goal for world domination. Dr. Druid would ask Bruce Banner to help him defeat the Maha Yogi. Both men enter the Maha Yogi's castle domain where they are attacked by his guards. Banner transforms into the Hulk but Dr. Druid exerts a subtle hypnotic influence to take over the Hulk's feeble mind. Dr. Druid orders the Hulk to capture the Maha Yogi but the powerful psychic uses his mental powers to battle Dr. Druid for the Hulk's mind. The Hulk's mind is overwhelmed and collapses. Mongu and the Maha Yogi overpower Dr. Druid and places both of his foes into the dungeons. The Maha Yogi provides some entertainment for his mercenaries by placing his bodyguard Mongu to battle the Hulk inside his arena. The Maha Yogi watches above while keeping Dr. Druid under his control. The Hulk begins to gain the upper hand during his fight with Mongu so the Maha Yogi decides to intervene. He would use his Jewel of Jeopardy to provide Mongu with more power. By devoting his energies to Mongu, the Maha Yogi unknowingly released Dr. Druid from his spell. Dr. Druid would control a piece of rope to grab the Maha Yogi's hand and he drops his mystical gem into the arena. The Hulk smashes his Jewel of Jeopardy and the Maha Yogi rapidly aged to a feeble, old man since the arcane energies could no longer sustain his psychic powers. His loyal servant Mongu picks up the Maha Yogi and vows to remain forever faithful while the rest of his mercenaries desert him.
The Maha Yogi and Mongu would reappear sometime later with two men named Chandu the Alchemist and Le Sabre. This group infiltrates the Avenger's mansion to seek out the ebony blade. The Maha Yogi manages to take mental control of Luna's nanny, Marilla but is defeated when he is struck by the Black Widow. The current whereabouts of the Maha Yogi are unknown.
Powers & Abilities
The Maha Yogi has vast mental powers and has displayed various psionic abilities, thanks to being genetically altered by the Caretakers of Arcturus; though he has sometimes been referred to as a mutant, he is not. He can control the minds of others, hypnotize his victims, induce hallucinations, create illusions and alter his appearance. He can place individuals under his mental spell and temporarily nullify their abilities with enough concentration.
He can also create psionic force bolt, sufficient to destroy small buildings. He can create force fields. He can teleport people over long distances and telekinetically move objects.
While posing as a magician for centuries, Mad Merlin initially had no magical powers. Simply simulating the effects of magic. More recently (in Captain Marvel stories), Mad Merlin seems to have started practicing genuine magic. For example transforming the Red Raven to an actual raven. How he compares to more experienced magic users is unknown.
Equipment and Weapons
The Maha Yogi once possessed a fragment of the Hellfire Helix that made him virtually immortal. He could use his mystical gem to increase his abilities or grant more power to various individuals.
The distraction of his fragment initially accelerated his aging process. He could well share the fate of his contemporary Ulysses Bloodstone who aged to the point of death. He has since visibly regained his youth. He might also have regained his immortality through magical means.