The Tower Of Masters is an Competition for Pokemon Trainers who have beaten all the gyms, Beat The Elite Four, and complete the national dex. They must also have Lv.50-100 pokemon.
They must battle the master of each type, "someone who is so good, they could beat Wallace, Cynthia, and Lance combined" says Proffesor Oak. The last person is Ikaka Washakhu, The God of Pokemon Training. He invented the art of battling pokemon. For this and only this, trainers may use up to 9 pokemon. Full Restores are the ONLY items allowed in this tower, any other item becomes uneffective. And for the first time in the HISTORY of Pokemon, there is a level 101, AKA level X, when a pokemon becomes indestructible without the Guardians