Meltie

A Meltie is a variation of a Stickie: it has a weak skin, and its only purpose is to break itself against enemies. However, it's much more deadly, because its internal fluids are highly acidic: it doesn't seem to have any effect on stone or metal, but it can dissolve organical matter (with the exception of bones) in a few seconds. The skin of a Meltie seems acidproof, but the Melties are seen generating bubbles on their skins which then explode, emitting small quantities of acid. The reasons of this procedure is unknown.