The main antagonist ofStreet Fighter IV. He is the head of Shadaloo's weapon division, S.I.N. According to the official Street Fighter website, Seth is one of many genetically engineered replacement bodies forM. Bison. Seth returns inStreet Fighter VasFemale Seth. With his body destroyed at the end of Street Fighter IV, his surviving brain is combined with the body of aShadaloo Dollnamed Unit Zero, resulting in Seth adapting a new female appearance.