Gem Cave Creature

The Cave Creature was a gem creature that inhabited a cave as seen in Arcade Mania and served as an antagonist.

History
At the start of Arcade Mania the gems were seen being attacked by the cave creature, which Garnet managed to defeat and take it's gem.

Trivia

 * It was revealed in the episode Ocean Gem that monsters the dropped gems were previously humanoid crystal gems that became corrupted.