Jason Wyngarde

Jason Wyngarde is a member of the Inner Circle Club and the main instigator of Jean Grey's corruption into the Dark Phoenix.

Biography
Wyngarde, wth help of Emma Frost, entered Jean Grey's mind and projected a dream world where Jean fell in love with him. Thanks to this illusion, they managed to have Jean join the Inner Circle. This made Jean's Dark Phoenix persona emerge, and she eventually eschewed the Inner Circle. When Wyngarde tried to use his illusions on her again, Phoenix didn't fell on them and forced Wyngarde to assume his true weak form.

Background
As the series' version of the X-Men had never faced Wyngarde before the Dark Phoenix saga, his "real form" doesn't have any real purpose besides being a nod to the comics.

In the comics
Wyngarde goes by the supervillain name Mastermind, but he doesn't use it in the series.

Was a founding member of the Brotherhood of Mutants.