Mimic

A mimic is a monsters that disguise himselves as treasure chests, waiting to leap out and attack unsuspecting adventurers. Since they set a trap by mimicking treasure chests, they usually live in places such as towers and caves, or other places where someone would likely find a treasure.

Even though mimics seems affected by substantial practical problems about ergonomics and locomotion, they have powerful illusion, teleportation, and pocket-dimension-hopping abilities.