If this first trailer is anything to go by, X-Men spinoff Legion will be unlike any TV series Marvel have produced to date. 

Although not associated with the timeline in the X-Men movies, Legion is connected by the fact that Dan Stevens' central character, David Haller is canonically the son of Charles Xavier/Professor X (portrayed by Patrick Stewart and James McAvoy in the movie franchise). 

Haller believes that he is mentally ill and that all the incredible things he can do are in fact in his head. In reality though he may just be the most powerful mutant ever. He also suffers from multiple personality disorder, with each personality having it's own unique ability. 

The series also stars Parks and Recreation's Aubrey Plaza and Fargo's Jean Smart and Rachel Keller.