Originally Posted by Guerrilla
Could also be Captain Marvel. Or maybe Quasar? Who knows. Im just guessing anyone with any kind of diamond-ish/star-ish type of emblem on them. Probably Vision though.
Including Mr. Sinister.
Keep in mind that Mayimbe doesn't specify a Marvel STUDIOS movie --- just a Marvel
I've also heard a suggestion that "diamond" could refer to Diamondback, who might actually wind up being the mysterious "female lead" role they've been trying to cast for CATWS.