Tabuu was the ruler of subspace. In Brawl, he tried to control both realms, but was beaten with Sonic and the rest of the smashers. In Super Smash Bros X, he kidnapped Meta Knight, Donkey Kong, and Bowser, turning them to his side. He eventually lost his new comrades back to the other side, but he had become stronger than ever. He died when Krystal ran her staff straight through the disc like object inside him.