When Kevin MacTaggert's mutant abilities manifested, his psionic energies burnt out his body. For this reason, Kevin's mother, Moira MacTaggert, placed him in a chamber of her own design to protect himself and others from his powers. During this time Kevin went mad because of his seeming endless suffering, getting a huge resentment against his mother and father. He started calling himself Proteus. After Proteus escaped confinement, he battled the X-Men members Phoenix, Madrox, the Multiple Man, and Polaris. who where at Muir Island at the time; Although he defeated Polaris and the Multiple Man quite easily, Phoenix nearly killed him.
Proteus however managed to possess one of Madrox's clones, and escaped from Muir Island using it, heading towards his father's house in Edinburgh. Using several host bodies in witch he could reside his own persona along the way. Problem was that the energies these host bodies had would soon run out (killing the host), thus Proteus needed more and more host bodies.
Along the way he encountered the X-Men, who were hot on his trail. Using only a fraction of his mutant powers, Proteus was able to easily defeat Storm, Wolverine and Nightcrawler. Eventually he made it to Edinburgh and took over his father's body. While possessing his fathers body, he battled the X-men. However, his powers soon burned out his fathers body, destroying it. Before he could possess another body, Proteus was punched by Colossus who's metal body disrupted his psionic energies and effectively killing him.
Sometime later, a woman by the name of Erika Benson (also known as Harness) was hired by AIM to use her son, Gilbert Benson, to collect the energies of Proteus for their own use. Gilbert had the ability to absorb the energies that were once Proteus, and his mother intended to collect it all. Her mission was almost thwarted by the New Mutants, New Warriors as well as Moira MacTaggert and a number of her mutants from Muir Island. Their intervention failed, and Gilbert's body exploded, resulting in a fusion entity that was both Gilbert Benson and Kevin MacTaggert.
This new Proteus used his powers to reshape Edinburgh, Scotland to his own whim. The inclusion of X-Factor to the battle soon took on a philosophical tone, as the group of heroes questioned the ethics of killing Proteus or trying to help them. In the end, Proteus realized that reality was not compatible with him and "killed" himself.
Kevin MacTaggert was created by Chris Claremont and John Byrne. Kevin MacTaggert made his first comic book appearance in the pages of X-Men #125. He made his first appearance in his Proteus persona in X-Men #127.
Major Story Arcs
When the Scarlet Witch restructured reality into the House of M she resurrected Proteus. Proteus was known as Mutant X and killed many people in his search for the perfect host body. Proteus came across the Exiles and became a recurring villain. He managed to escape his own reality, and began hopping from dimension to dimension searching for a body that would not burn out. All this time the Exiles where close behind him, trying to stop him. He possessed and killed many people including Mimic .
After killing Mimic he possessed Morph. He learned that Morph could withstand his psionic energies indefinitely and found his perfect host. That is when he began to formulate how to rule every dimension in the multiverse. The rest of the Exiles devised a way to subdue Proteus and attempt to bring back Morph. The Exiles brainwashed Proteus into thinking he was Morph and for several missions they had him convinced that they defeated Proteus and that he (Proteus) was Morph. This way the Exiles could keep an eye on him without worrying. Eventually Morph's real persona re-appeared and took control of his own body again. Closing Proteus in a small part of himself, but agreeing to 'live together inside him.
For More Information: Necrosha
Kevin MacTaggert returned during the Necrosha story arc. When Selene resurrected Destiny, Proteus some how appeared inside her. Destiny tried to communicate with her foster-daughter Rogue, but some how she got Blindfold instead. Proteus quickly possessed Blindfold and tricked her into convincing a bunch of gathering X-Men ( Rogue, Trance, Psylocke, Husk, Colossus, Magneto and Nightcrawler) to go to Muir Island.
There he revealed himself to them and was able to defeat them quite easily, Proteus gained a new ability where he can possess more than one, he was able to possess Trance, Psylocke, Nightcrawler, Destiny, and Husk. While possessing the group, he forced them to fight Rogue and Magneto . Magneto, still weakened, used the last of his strength to launch himself and Proteus (who was possessing Blindfold) into the upper atmosphere. He had enough time to analyze Proteus' psionic energies. Magneto determined that he could affect Proteus' energies, disrupted them and made Proteus disappear. Magneto confirmed that Proteus is most likely not dead, but that his energies are merely dispersed, saying that he will be able to reintegrate himself one day. Magneto was hoping that he spread Proteus thin enough to prevent or at least postpone his return for a long period of time. Whether or not Proteus' energy remained after Necrosha ended (witch meant all resurrected dead where put to rest again) remains to be seen.
Powers & Abilities
Proteus can generate enormous amounts of psionic force from his energy state that allows him to restructure reality in any manner. He exists as an energy form that can inhabit human bodies to contain his energies, however any body he possesses quickly begins to break down so he constantly needs new host bodies. Metals disrupt his energies, so Proteus cannot possess certain bodies, such as Wolverine's, because his body is full of adamantium. Proteus has shown to be able to possess more than one body, as shown him inhabiting the body's of Trance, Blindfold, Destiny, Psylocke, Nightcrawler, and Husk all at the same time.
In the Ultimate Universe he is the son of Moira MacTaggert and Professor X and his name is David Xavier. As he grew up he enjoyed sports and video games and was unable to relate to his intellectual father; because of this he felt that Charles disliked him. Charles left with Magneto to form the Brotherhood Of Evil Mutants and left David disliking him even more. The next day his powers began to manifest. He left to search for his father inhabiting bodies of anyone he saw and going to a new one as the host body's energies wore out.
He was eventually confronted by the X-men and his parents and he took control of Wolverine's body knowing that Wolverine's healing factor would counteract David's energy drain. Just before getting hit by a truck he left Wolverine's body and eventually found his way to the body of Betsy Braddock, or Psylocke. He then taunted Charles and was ready to kill him but Betsy's mind resurfaced and blocked David's powers. Colossus then crushed Betsy and David beneath a car, killing them both. Betsy's mind was later transferred to a new body and she was reborn. David is still believed to be dead.
In Other Media
X-MEN:The Animated Series
Proteus appeared in Proteus, Part 1 (Episode 49) & Proteus, Part 2 (Episode 50). He is voiced by Stuart Stone