We negotiated with a gargoyle once. While we were trying to talk, he would pop gold coins into his mouth like candy. We never got those back when he died.
Looked back and saw this thread started in 2006? Anyhoo...
Monsters that Eat Gold
Black Puddings & several oozes: dissolve (aka eat) metals Xorn: eat precious metals Aurumvorax: as already noted, another 1st edition monster there to teach players to keep their cash in a bank Bag of Devouring: yeah, it's a cursed item, but it eats your well earned gold in a way
Other creatures were referenced, but they don't eat gold and instead mimic it. These include:
Hoard Scarab (Draconomicon): swarming beetles that look like gold coins
Lock Lurker (Dragon Magazine #139): a stinging creature that looks like a gold coin
Goldbug (Fiend Folio): looks like a gold coin but really a deadly poisonous monster