The Legion ending definitively concludes David Haller's story after three seasons. The FX series chronicled the life of David Haller, the mutant son of Charles Xavier whose life was thrown off course when he was possessed by the monstrous Shadow King when he was an infant. The Shadow King - real name Amahl Farouk - was a powerful mutant who attempted to lull Xavier into a trap, but he was defeated by the future X-Men leader. Xavier thought he had vanquished him, but Farouk's essence survived and attached itself to baby David.
The combination of David's mutant abilities and mental illness, as well as Farouk's influence, made him a dangerous, unpredictable force, and by the end of season 2, David had become Legion's antagonist rather than its hero. He's spent most of the third and final season attempting to reset the timeline to suit his own needs, so that Farouk would never haunt him; he could then, presumably, lead a better life. But that mission has resulted in David crossing lines he never would have before, going so far as to murder his former friends and colleagues, which he justifies by claiming the current timeline to be false.
With the help of mutant time traveler Switch, David was indeed able to arrive in the past just before Xavier and Farouk had their fateful confrontation, fully intending to kill Farouk and reclaim his freedom. Surprisingly, David ended up getting what he wanted in Legion's ending, but not in exactly the way he thought he would.
Professor X Saved David After All
While this may be a younger, rawer version of Charles Xavier than we're used to seeing, he's still fundamentally the same man. While he initially agrees to help David kill Farouk, the reluctance to take a life is written all over his face; it's no surprise that Charles decides to find another way. With David engaged in combat with the past Farouk, the present Farouk and Xavier share a drink in the astral plane, as the former explains to the latter who his son has truly become.
Farouk, in his own way, cares deeply for David, as they shared the same mind and body for decades; he developed a twisted sort of paternal love for the man he slowly drove insane out of revenge. After Farouk shared his plan with Xavier, David was recalled to the astral plane, where he finally has the talk with his father he's needed all his life. Devastated at the very notion he could ever abandon his son, Xavier promises David that he loves him deeply and will do everything he can to protect him and give him a good life; it may be Legion's most emotionally arresting moment.
Meanwhile, Syd and Cary find themselves transported to David's childhood home, where they find Gabrielle and baby David himself. Switch - revealed to not just be a mutant, but a fourth dimensional being as well - sent Syd there as a final gift; she's able to convince Gabrielle that what David needs more than anything is the love of his mother, and that she must devote herself completely to her child despite her own deep, mental scars she endured during World War II. Through two very different avenues, the once-orphaned David was now primed to be raised by two loving, present parents.
The Two Farouks Explained
Present-Farouk promised Xavier he could end the vicious cycle that had caused both David and himself so much heartache over the years. Once Xavier convinced David not to kill past-Farouk, all four players returned to past-Farouk's estate. Past-Farouk was still adamant about killing Xavier until present-Farouk, noting the immaturity of his past self, hands him a pair of sunglasses. In a matter of seconds, past-Farouk gets a highlight reel of the next three decades that drives him to openly weep. Once he realizes he will eventually come to love this boy he's about to destroy, past-Farouk abandons his violent plans and declares a truce with Charles and David.
Legion's exploration of Farouk - both past and present - is one of its greatest achievements. After spending season 1 as either a yellow eyed nightmare monster or Aubrey Plaza, Navid Neghaban took on the role in season 2 and immediately infused the character with a sort of effortless charm that managed to obscure his darker impulses. Amazingly, Legion was eventually able to credibly make this character - this monster - into someone audiences were willing to embrace and root for. It's perhaps the best magic trip Legion ever pulled, which is saying something.
Legion's Timeline Reset: What Happens To David?
After the confrontation with Farouk, the time travelers begin to fade away, as the Legion timeline changes mean that version of the future no longer exists. The final two people to vanish are David and Syd; the former lovers stand over baby David's crib, contemplating everything they've been through together - the passion, the betrayals, the acceptance. Syd - always Legion's most clear-eyed, morally pure character - bids adult David a final farewell with a hint of a warning as they disappear: "Be a good boy."
Despite all his transgressions, David eventually gets what he wanted. It's tempting to interpret this outcome as Legion saying the ends justify the means, but that's not what's happening here. David was at least partially right - the timeline was indeed corrupted, but not necessarily in the way he thought. David is a deeply, pathologically selfish person, essentially unable to empathize with anyone if it means contradicting his own beliefs. This led him to dark places, and the fact that he gets off scot-free feels like a slight from the wrong angle. But the point was never to save David; it was to save everyone else.
With the Legion timeline reset, David will have a life free of Farouk's influence and with two devoted parents, but that's no guarantee he won't be haunted by madness. As Legion progressed, David exhibited mental issues beyond Farouk's influence, something akin to schizophrenia. He's still destined to be a powerful mutant, so he could very well end up on a surprisingly similar path.
But Sydney Barrett will likely never meet David in an asylum, and she will never be violated and betrayed by him. Charles Xavier now realizes how fragile his wife's psyche is, and resolves to stay close to home and strengthen his family rather than galavanting around the world looking for more mutants; he even mentions he wouldn't mind being a teacher. Everyone gets a second chance now, and if the price is that David gets one too, that seems worth it.
There's never been a comic book adaptation quite like Legion, and there may never be again. With Disney's purchase of Fox, the House of Mouse now controls the future of the X-Men and their associated characters on the big and small screens. That will almost certainly result in some great, crowd-pleasing fare, like the rest of the Marvel Cinematic Universe. But the next time you're watching a multi-million dollar spectacle, spare a thought for the kind of innovative, visually masterful storytelling that Legion represents, and remember that these characters can sometimes do more than entertain - they can transcend.