X-Men movies aren't exactly known for their villains. Despite having a number of awesome baddies to choose from, the movies almost always pick Magneto. The films have recently started shifting towards different villains since they realized they can't use Magneto for 20 years, last year we got Apocalypse who… well, let's just say they didn't do a super great job of portraying him.
Next year, Fox will release their next main entry in the X-Men series with Dark Phoenix which sees Jean Grey turn against the X-Men. The story was previously adapted in X-Men: The Last Stand but Days of Future Past seemingly wiped that out of the cannon. Game of Thrones' Sophie Turner will return as Jean Grey but another red-headed actress is also joining the cast in an unspecified role.
Jessica Chastain will officially be joining X-Men: Dark Phoenix after many rumors which suggested she may be playing Lilandra, an ally to the X-Men. However, Chastain's newest Instagram post suggests that she may actually be a villain. Due to her likeness to Jean Gray, it's possible that she may be playing an older version of the character or a relative. We really have no idea who she could be playing.
X-Men: Dark Phoenix will release on November 2nd, 2018 and will be directed by long-time X-Men producer, Simon Kinberg.