The first season of Legion has felt like a prologue of sorts. David Haller (Dan Stevens) meets a group of enhanced individuals and discovers that he's been living under a under a few misconceptions: That his parents are his biological parents; that the voices in his head are symptoms of schizophrenia; and that there isn't a malevolent mutant monster who's been feeding off his thoughts and memories since he was a baby. Season 1 of Legion has been David's origin story. The finale airs March 29, and FX has already renewed Legion for Season 2. Where might this troubled young mutant's story go as the show continues? A look at what happens to David Haller in Marvel comics will present some possibilities.
I say possibilities because Legion has already deviated considerably from the comics on which it's based. In the books, David develops what appears to be a dissociative identity disorder when he's a victim of a terrorist attack and absorbs the identity of one of the bombers, Karami. The blast also creates psychic linkage between David and the rest of the blast's victims. All those memories and all that pain is too much for one mind to bear, so he becomes catatonic and is eventually entrusted to the care of Moira MacTaggart, the human geneticist played by Rose Byrne in the recent X-Men movies. David's many mutant powers are then divided between his multiple personalities.
Meanwhile, Karami's consciousness is desperate to become independent again. Once it does, Karami reads David's mind and determines his host's innate goodness. He attempts to heal David's psyche and reincorporate his legion of personalities back into one. But a few of those personalities are too stubborn and they resist the absorption: the telekinetic Jack Wayne and the pyrokinetic Cyndi. They, along with Karami, battle for control of David's mind, the core of which is still the young boy who was caught in the blast. And there, the show's focus on David's youthful fear and confusion matches up with the comics.
Because of his sensitivity, David (or Legion, at this point) is highly susceptible to possession. The Shadow King takes advantage of this, just as he does in the series. It's not clear in Legion what the Shadow King's motives are exactly. In the comics, he uses David's body and telepathic mind to spread malevolence and evil.
If the show continues to follow the path set by the comics, David won't be a hero, or at least a spotless one. Because of the troublemaking identities constantly jockeying for power in his brain, Legion is at odds with the X-Men in most of the series in which he appears. He accidentally creates the Age Of Apocalypse timeline when he attempts to kill Magneto on behalf of his biological father Charles Xavier and kills Charles instead. His personalities begin to hunt for companions, killing people and adding to his collection of identities. They even obtain their own bodies at one point, no longer limited by being trapped in David's in the damage they can inflict.
David does fight the Nimrod Sentinels alongside the X-Men in the "New Mutants" series, and various X-Men try to help David by various means, including invading his consciousness and killing off the worst of his personalities. But it's like attacking an army, and his mind has defense mechanisms it's developed to fight off its enemies. One of those mechanisms is a super-personality powerful enough to create a new universe where David is beloved as a do-gooder, a dream of his that can never be fulfilled. Ultimately, David decides that the only way he can avoid doing harm is by using his Legion abilities to remove himself from reality.
David Haller's story is twisty and tragic, an allegory for the push-and-pull of mental illness and the death grip of childhood trauma. If Legion follows the spirit of the comics, the telekinetic anti-hero is in for some rough times.