'Legion' Primer: What to Know Before the Season Finale

Here's everything to know about the first season of Noah Hawley's X-Men series, before heading into the final episode.
Chris Lang/FX

[Warning: This story contains spoilers from the first seven episodes of FX's Legion.]

It's hard to wrap the mind around Legion, the FX and X-Men series from Fargo creator Noah Hawley. Blame the multiple levels of reality, the battles being waged within series lead David Haller's (Dan Stevens) fragile mind, for the show's level of complexity. Add the words "Shadow King," as well as a surprise appearance from a man who looks like Two-Face in the penultimate episode of the season, and you can be forgiven for needing a dose or two of your favorite headache medicine.

There's only one episode left before Legion goes dark, signaling the long wait until season two. Before that happens, THR rounds up what to know heading into the finale:

• After spending his entire life wrestling with mental illness, David Haller's world explodes with the revelation that he's actually an all-powerful telepathic mutant. He explores the extent of his powers thanks to Melanie Bird (Jean Smart) and the others at Summerland, a facility designed to help mutants understand their abilities. During his time here, he grows closer to his girlfriend and fellow mutant Syd Barrett (Rachel Keller), while simultaneously wrestling with a monstrous presence that lurks inside his mind.

• As it turns out, that menace of the mind, traditionally known as Lenny (Aubrey Plaza), boasts a few other identities as well: the Devil with the Yellow Eyes for one, and the World's Angriest Boy for another. All these names pale in comparison to the big one: Amahl Farouk, better known as The Shadow King, an iconic X-Men villain created by the legendary comic book duo of Chris Claremont and John Byrne. The Shadow King, much like David, boasts all-powerful psychic abilities — hence the carnage Lenny has wreaked over the course of the season.

• Cary Loudermilk (Bill Irwin) and Oliver Bird (Jemaine Clement) are the geniuses who uncover the Shadow King's true identity, but David is able to figure out what's going on with the help of a friendly face — his own. In the penultimate episode of the season, Stevens goes full Matthew Crawley, appearing with his natural British accent as the logical side of David's personality. He coaches David into realizing that the Shadow King was an old enemy of David's real father, and has been burrowing into our hero's consciousness ever since he was a child. All those bitter memories about King the dog and the Angriest Boy? David has the Shadow King to thank for all of that. What's more, he can thank himself for realizing the truth about his inner demons, giving him the power to fight back.

• In order to defeat the Shadow King once and for all, the Summerland mutants must place a device on David's head that will isolate the psychic parasite. Only problem: Lenny beats them to the punch, placing the Summerlanders in a fantasy version of Clockworks where the Shadow King reigns supreme. By the end of "Chapter 7," however, an empowered David is able to break free from this world and place the veritable crown on his head, keeping the Shadow King at bay, at least for now.

• As our heroes return to Summerland to eradicate the trapped Shadow King once and for all, they run into some unexpected adversity: Division 3, the government organization tasked with tracking down David and his fellow mutants. And no, that's not Harvey Dent leading the charge, as much as he looks like the old Batman foe. Instead, that's the same interrogator played by Hamish Linklater in the Legion pilot, looking considerably worse for the wear after suffering through the first episode's closing firestorm. Just as he arrives, viewers start to see David's control over the Shadow King growing weaker and weaker — awful timing for an already awful situation, as Legion moves steadily toward the final act of its first season.

• Oh, one more thing to know: Once the finale ends, stick around through the credits, or else risk missing out on one last what-the-Hawley moment.

What are your predictions for the Legion season finale? Sound off in the comments below, and follow THR.com/Legion for interviews, news and more.