Fargo actress Rachel Keller has reportedly been cast as an unnamed lead in FX's Legion series, according to Deadline. Based on the X-Men character of the same name, Legion was previously announced (along with Hellfire) as two new live-action series 20th Century Fox was developing with assistance from Marvel TV.
According the the Hollywood trade, Keller's role will be a "scrappy, optimistic woman in her 20s." Deadline goes on to say that the character might have mutant powers related to human touch, citing Rogue and Spyke as parallels.
Deadline's description of Legion is close to the character's comic book origins, as son of X-Men founder Charles Xavier. David Haller is said to have "struggled" with mental illness since his teenage years, living "in and out of psychiatric hospitals for years" after being diagnosed as schizophrenic. A "strange encounter" with another patient prompts Haller to consider that "the voices" in his head could actually be real.
Fargo's creator Noah Hawley is acting as showrunner of FX's Legion, with Bryan Singer, Lauren Shuler Donner, Simon Kinberg, Jeph Loeb, John Cameron and Steve Blackman all onboard as producers.