I liked cubo's idea but not a lot so here is my idea: Matter (at the time) was a knight based character in a game, before his sprite glitched, leaving him unusable, his creator abandoned him, and over time, the "? block" made him realize, he wasn't real... He figured it out, he realized nothing "mattered" so he fused with a block, a hole in his face instead of a real visor, he killed all who he saw, because after all if they aren't real, then why do there life's matter, so with this new knowledge (and a need for a rebrand) he had become. "AntiMatter"
