In the Gym Leader Castle, the player is challenged to collect Gym badges by defeating trainers at the eight Johto League Gyms. Pokémon battles follow the same three-on-three format as in the Stadium, and either imported or rental Pokémon may be used to construct a team of six. Each Gym is known for using a specific type of Pokémon, but the Gym's trainers can have Pokémon of a different type for balance. The Elite Four can be battled after collecting all eight badges, and upon their defeat, a rival battle is unlocked. Defeating the rival unlocks the Kanto Gym Leaders and subsequently the Pokémon Champion Red.