Unlocks: Swarm’s “Bee is for Butt Stinger” Ability
Make your way through the carnival until you reach The Promenade, and prepare for a big battle.
Once you’ve cleared the area, the Battle Gate will drop. Head up the stairs and make a u-turn, and follow the ledge around to the left.
Follow the path to find a Soul Gem hanging out on a grassy knoll.