Gift from Kahili
Outside of the Pokémon League, you don’t really get a chance to see Kahili, the Flying-type expert. Well, there was that time she randomly appeared out of nowhere after obtaining Flyinium Z. Anyway, you’ll find her loitering around in the lobby of Grand Hano Resort. Speak to her to receive TM92 Trick Room.
Does it sometimes bother you that some Pokémon are slow beyond belief? If you use Trick Room, for five crucial turns, the speed priority during battles is reversed so that slower Pokémon move before faster Pokémon. This enables your slow-moving juggernauts to potentially sweep faster and often fragile foes.