Quoted By:
Ghost.
Drifblim. Substitute, Minimize, Baton Pass, Astonish.
Shedinja. Toxic, Protect, Confuse Ray, Phantom Force
Mimikyu: Astonish, Swords Dance, Attract, Confuse Ray
Astonish is your TM.
There's no puzzle. The gym is just a long corridor filled with trainers with level 5 Mimikyu and Prankster Sableye.
The badge is a piece of foil with "SPOOKY" written on it.