A
NetHack monster that
ambushes unsuspecting
players inside
shops. It assumes the form of other items that are around it, so it is nearly impossible to detect before you stumble over it and it tries to
kill you. Comes in three varieties: normal, large, and giant. The large and giant versions exude a sticky
glue that makes
escape impossible once the creature is engaged.
Mimics can occasionally be identified prior to the ambush by looking at the shop's merchandise carefully. An item that seems out of place (for example, a potion inside an armor dealership) is probably a mimic.
And yes, the shopkeeper will charge you for the corpse, as well as any items you break during the struggle.