In his capacity as referee of the Upstarts' games, the Gamesmaster oversaw the Upstarts' activities, which included confrontations with the team of adolescent mutants known as the Hellions and the team of superhuman mutant adventurers known as the X-Men.
Later, the Gamesmaster took possession of both Doctor Weisman of the Weisman Institute for the Criminally Insane and one of the patients, a young boy named Jeremy Stevens.