the u.s. version has introduced numerous modifications, or "twists", on the core rules in order to keep the players on their toes and to prevent players from relying on strategies that succeeded in prior seasons. these changes have included tribal switches, seasons starting with more than two tribes, the ability to exile a player from a tribe for a short time, unannounced returning players, hidden immunity idols that players can use to save themselves or others at tribal council, special voting powers which can be used to influence the result at tribal council, chance to return to regular gameplay after elimination through the "redemption island," "edge of extinction" or "the outcast tribe" twists, and a final four fire-making challenge as of season 35.