Biff is a member of the Sakaaran Rebellion, who was forced to become one of the Grandmaster's champions. During the Escape from Sakaar, Biff joined Korg and Miek on a slave revolt. Later, he participated in the battle against Hela and survived.
Because of various circumstances, Biff left his home planet and ended up on Sakaar. Biff was forced by the Grandmaster to become one of his champions and fight at the Contest of Champions. While Biff was casually waiting for the next fight, Sakaaran Guards brought Thor to gladiators' quarters where he talked with Korg about the Contest.
Eventually, Valkyrie stormed the gladiators' quarters and provided Korg with a weapon, initiating the Sakaaran Rebellion. Biff fought alongside his fellow gladiators against the guards and they ultimately reached the Grandmaster's garage. Accepting Loki as their leader, Biff and the other rebels seized the Statesman and flew it to Asgard.
The Statesman ultimately arrived near the Rainbow Bridge. Biff got off the spacecraft with his fellow rebels and began attacking Hela's Berserkers so that the Asgardians could escape Hela's tyrannical rule. He survived the destruction of Asgard, along with the the remaining Asgardians, who fled to Earth on the Statesman.