Pokémon Ruby and Sapphire/Mt. Pyre

Mt. Pyre is a place where people gather to remember lost Pokémon. Since this is a cave, anywhere you step can result in a battle. Make sure you avoid the holes in the floors. Climb the mountain until you reach a grassy ledge with stairs leading down to a rocky ledge. Here you'll find TM48 (Skill Swap).

Wild Pokémon
Duskull, Shuppet