First appearance of Juggernaut. Juggernaut, also known as Cain Marko, is Charles Xavier's half brother in the series. He is identified by Cerebro as having an enhanced mutant signature. Xavier confirms that this version of Juggernaut is a mutant, but his latent X-gene was activated by mysticism. This differs from his comic counterpart, where Cain is Charles' non-mutant stepbrother who gains his powers from the Crimson Gem of Cyttorak.