Mimic

In the Dungeons & Dragons fantasy role-playing game, the mimic is a type of fictional monster. It is portrayed as being able to change its shape to disguise its body as an inanimate object, commonly a chest. The mimic made its first appearance in the original Monster Manual (1977), by Gary Gygax. This book described mimics as "subterranean creatures which cannot stand the light of the sun. They are able to perfectly mimic stone or wood." According to the book, mimics thus pose as items such as stonework, doors, or chests; when a character or creature touches the disguised mimic, the mimic can lash out with a bludgeoning pseudopod. A mimic excretes an adhesive glue to hold fast whatever touches it.
(Wikipedia)