Hag
The Hag is a creature that bothers Finn and Jake in the episode “City of Thieves” taunting Finn and saying that he will become a thief when he enters the city. The Hag has an ability of becoming flat and making herself look just like the ground. She appears twice in the episode, first in the forest next to the City of Thieves, and next on the ground next to the Palace of Thieves near the end of the episode. She promises at the beginning that Finn will walk out of the city a thief, though Finn purifies himself. She is the sister of the Tree Witch and is very similar to her.