Mastermind the evil alter ego of carnival mentalist Jason Wyngarde has been troubling the X-Men since Stan Lee and Jack Kirby created the character way back in 1964. His main mutant power is to cast convincing illusions, and he can fiddle with peoples memories too. Wyngarde was first introduced as a member of the Brother Of Evil Mutants. He helped the sinister collective nab control of a South American country, by creating an illusion that looked like an army of thousands. This gives you an idea of the sheer scale of Masterminds abilities, which could make him an difficult foe for the cinematic X-Men. The possibilities are endless with illusions, really, and it hasnt been explored all that much in superhero cinema. A few moments in X-Men 2 and Avengers: Age Of Ultron have teased the idea, but audiences have never seen the havoc a deceptive trickster like Mastermind could wreak on a global scale. Youd need a skilled actor with a wide range to pull it off, and to stop the character from coming across as cheesy. Michael Madsen would be ideal, especially since The Hateful Eight proved that hes still at the top of his game. In that Tarantino western, he gave an ambiguous and untrustworthy performance, which is exactly the kind of persona that Mastermind would need.