|The Crystal Eye in the dungeon|
The Crystal eye is a giant crystal hidden deep within the Dungeon; its only appearance is likewise in "Dungeon." The crystal eye serves to cover a hole containing Demonic Eye Creatures. It is unknown whether the crystal eye has any real value, but Finn probably wanted to retrieve it in the spirit of adventure.
It looks nothing like an eye; it resembles a huge, faceted blue gem. The crystal eye is of immense weight, consistent with its size, requiring both Finn and Jake to lift it simultaneously.
- It appears in Adventure Time: Hey Ice King! Why'd you steal our garbage?!! as a usable item. It grants temporary invincibility.