Giant Goo Skull

The Giant Goo Skull is a giant monster appearing in "Vault of Bones".

In "Vault of Bones", Flame Princess started wrecking havoc in the dungeon full of bones. While wrecking havoc, she angered a legion of goo skulls. which attacked her. She easily defeated them, due to their goo being explosive. However, the Giant Goo Skull appeared and captured Finn, taking him away. After Flame Princess noticed this, she went after the giant.

The monster started wrapping Finn in its goo. Flame Princess ordered him to let Finn go, but the Goo Skull didn't accept, angering Flame Princess. However, instead of killing the monster, she made him do the splits (like Finn previously did against a skeleton). Then, Flame Princess freed Finn goo he was wrapped in.