Crystal Guardian

The Crystal Guardian is a species of creature that has made two different appearances in two different locations and facilities: one as the guardian of the Crystal Gem Apple of the Evil Forest, the others as the guardians and protectors of the Crystal Dimension.

Crystal Guardian of the Evil Forest
The initial Crystal Guardian is first seen in Tree Trunks. It resides in the Evil Forest and guards the Crystal Gem Apple. It mirrored Finn and Jake by shaping into a similar crystal-like form of them, and then mirrored their actions making it invulnerable to injury. Finn and Jake tried to defeat it by physical force, but they failed. Tree Trunks then started dancing, and the Crystal Guardian began mimicking her. Finn and Jake decided to fight the monster "Tree Trunks style", by wearing makeup and asking politely if Tree Trunks could eat the apple. It is unknown if there is a limit to how many people and creatures it can mimic at once.

Creatures and people that were mimicked include:
 * Finn
 * Jake
 * Tree Trunks
 * A few Butterflies

In the Crystal Dimension
In "Crystals Have Power", Tree Trunks returns as Quartzion the Crystal Queen, the evil ruler of the Crystal Dimension, and assigns three Crystal Guardian minions to kidnap Finn and transform him into a crystalline form. Unlike the guardian of the Apple, these Crystal Guardians can talk and do not exhibit mimicry powers. Although they love and worship Tree Trunks, she did not think their love was enough, resulting in her quickly disintegrating them with her crystal powers.