Cavity Demon

The Demon Octopus is the main antagonist in the episode Meatball Party.

It lives in Raven's tooth and ate all the Titans after being free when the tooth cracked. It would attack every time Raven opened her mouth. Inside Raven's mouth, the Titans fight the Demon Octopus but are having much trouble, until Cyborg seals the tooth back up with meatballs, banishing the Demon Octopus back into the tooth (presumably).