Sigma is the primary antagonist of the Mega Man X series. He serves as the final boss in all mainline games in the series, except Mega Man X8 where he is the penultimate boss in Normal and Hard mode. Once the noble leader of the Maverick Hunters, Sigma fell into insanity and turned Maverick himself, becoming the leader of all haywire Reploids and waging war on humanity. Although he has been destroyed countless times, Sigma's programming always survives and finds a new form.