I do know there's only one (for me anyways) trainer in the Grand Hall that you can fight after defeating Corey and before Shade. Anyone is free to correct me on this though. Psychic Silva Mawile- Level 35- Iron Defense, Baton Pass, Crunch, Feint Attack Xatu- Level 36- Wish, Air Slash, Confuse Ray, Psychic Sneasel- Level 39- Screech, Slash, Beat Up, Hone Claws