is the main antagonist of the Mega Man X video game series. Created by Dr. Cain, Sigma was considered the finest of the Reploids and was the first leader of the Maverick Hunters, peacekeeping androids who defend humans against their renegade counterparts. Although he was once respectable, Sigma unexpectedly goes berserk during Mega Man X and rebels against humankind after coming into contact with the Maverick Virus. He defects to the Mavericks and assumes the role of their leader. Due to the virus integrated into his circuits, he can survive seemingly anything, and constantly returns to menace the world. Sigma has appeared in almost every Mega Man X video game since his first appearance in the 1993 title Mega Man X. He has received praise from critics and fans for his design and charisma as a villain, though his introduction was noted as marking a darker and more pessimistic theme for Mega Man X compared to other Mega Man sub-series. Characteristics Sigma appears as a tall, bald humanoid in most of his forms. As the former leader of the Maverick Hunters, Sigma is a capable military leader, rendering him a devious and strategic opponent to his primary enemies, X and Zero. Sigma is a skilled and charismatic manipulator, managing to turn various Reploids, Maverick Hunters, and Mavericks to his side. Although he has been destroyed countless times, Sigma's programming always survives, either building himself a new form, or is revived by Reploid and Maverick admirers alike; it is implied that he grows more insane with each revival. He is fond of incorporating himself into battlesuits which are vastly larger than his "regular" form. He serves as the final boss in all games except Mega Man X: Command Mission and Mega Man X8 (he does not appear in the former and in the latter, Sigma is the penultimate boss). History Mega Man X series Prior to the first Mega Man X game, Sigma was the most advanced Reploid of his time, leading the Maverick Hunters. However, one day, the Maverick Hunters received reports of an overwhelmingly powerful "Red Maverick" that destroyed an entire squadron of Hunters. While investigating, Sigma, along with his unit, tracked it down to an abandoned laboratory and faced the Maverick alone. The Maverick is revealed to be Zero, an evil robot created by Dr. Wily that carried a computer virus called "Maverick Virus". After Sigma defeats Zero,