Deadline has learned that FX's "Legion" pilot has added one more name to its cast: Amber Midthunder. Deadline describes Midthunder's character, whose name is Kerry, as "a woman of action with a childlike sense of wonder. A true savant, Kerry has lived a sheltered, but never dull life."

The pilot comes from "Fargo" showrunner Noah Hawley and will star "Downton Abbey's" Dan Stevens as David Haller, the son of Charles Xavier and a man with mental illness and haunted by voices in his head. "Legion" will also star Aubrey Plaza, Jean Smart, Jeremie Harris and Rachel Keller.

Like the rest of the previously announced characters, Midthunder's Kerry does not appear to have been based on any character from the X-Men comics. "Legion" is in development at cable network FX, with Hawley on board as a producer. According to the official description, "Since he was a teenager, David has struggled with mental illness. Diagnosed as schizophrenic, David has been in and out of psychiatric hospitals for years. But after a strange encounter with a fellow patient, he's confronted with the possibility that the voices he hears and the visions he sees might be real." Production on the "Legion" pilot will begin in March.