Queen Entozoa

Queen Entozoa was the female queen shown in "The Fancy Party". She was dying so she hosted a party and said that she would bequeath her power to the toughest of villains. In the end of the episode, it is revealed that her "power" and true identity was a slug-like demon that was possessing her body for 1,000 years and needed to switch bodies so it could possess a new body for another 1,000 years, however it accidentally became a sandwich for 1,000 years due to Wander's meddling.