In Pokémon Colosseum, the game's final battles take place here. After Wes and Rui reach the top, Nascour makes Wes fight all four of the Trainers inside the Colosseum, all of whom have a Shadow Pokémon, being Miltank, Absol, Houndoom, and Tropius. He then challenges Wes himself, saying that he might be a valuable ally to their Shadow Pokémon, and allowing for a quick heal. Nascour will bring a Shadow Metagross along to attempt to defeat Wes. Once he is defeated, he appears to apologize to his secret leader, which Wes and Rui question about. Evice, the secret leader of Cipher, appears and challenges Wes, after revealing his true identity and allowing another heal. He brings the ultimate Shadow Pokémon created along, a Shadow Tyranitar. Once defeated, Chief Sherles and Officer Johnson appear to arrest him. Duking, Silva, Eagun and his Pikachu arrive as well to say that Cipher is finished. Evice refuses and attempts to escape the newly arrived police via helicopter, but is thwarted by Ho-Oh's Sacred Fire.
After defeating Evice, the Trade machine is unlocked, allowing the player to trade between Pokémon Colosseum and the Generation III games.
The Realgam Colosseum is a glorious stadium built in the center of three mechanical towers. The Colosseum itself is a gigantic, open dome, with bleachers for spectators to watch. There is a giant Poké Ball shaped circle in the center the battlefield. The Colosseum itself is surrounded on almost all sides by vast, complicated networks of large towers of varying sizes.
The order of the Pokémon in a Trainer's team may be somewhat randomized when the player battles them. Therefore, depending on which Pokémon ends up in the last slot of their party, the Trainer's prize money may also vary.