Cherish Ball

The cherish ball isn't like the one in the main games. It contains one of the following legendary Pokémon: Articuno, Moltres, Zapdos, Suicune, Entei, Raikou, Regice, Regirock, Registeel, Xerneas, Celebi, Yveltal, or Volcanion (all will be level 40). A Cherish Ball is obtainable from a Treasure Chest (low chance).