Jon Hamm was at one time set to play Mr. Sinister a cliffhanger scene of 20th Century Fox's New Mutants, according to The Tracking Board. Director/co-writer Josh Boone reportedly filmed scenes leading up to Hamm's reveal in the role, however the studio reportedly changed plans.
Mr. Sinister was teased during X-Men: Apocalypse with the reveal of the name 'Essex Corporation'.
Now, according to the news site, Antonio Banderas is slotted in to play an unspecified villain revealed at the end of New Mutants.
Hamm was previously rumored to be courting Warner Bros. for the Batman role should there be an opening.