|Introduced in||"The Enchiridion!"|
The Heart Beast appears in "The Enchiridion!." It was one of Finn's many trials, given to him by the Dark Magician. He killed it by punching it repeatedly until it exploded (and spewing blood in the process). The Dark Magician claims that it is "completely evil."
The heart beast has no face but it has a purple glowing skeleton arm, a scarf, and strongly resembles a human heart.
- This is the only episode thus far that displays profuse amounts of blood, shown when Finn repeatledy punched the Heart Beast which splattered blood across the screen.