After making quite a splash in her role in Fargo season 2 Rachel Keller is set to be the female lead on Legion a Marvel property.
The pilot set in the X-Men universe is from Noah Hawley, Bryan Singer, Marvel TV and FX Productions. Not much is known about her role though she is described as optimistic and scrappy.
Legion is set around the character of David Haller the son of Professor Xavier. He struggled with mental illness since he was a teenager later diagnosed as a schizophrenic, he is also one of the most powerful mutants on earth.