Spoilsbugs are fist sized black beetles which normally burrow through the earth like moles and live on all kinds of minerals which they chew up with razor-sharp mandibles.
Whilst they eat all metals, their favorite food is gold, silver and other precious and semi-precious metals. The will also nibble on rock with high metal contents. They will also eat most crystal (like gems and crystal).
They are very slow walking about. They tunnel through stone at about the same speed. However, they are relentless.
They can give a nasty bite with their mandibles, although they only ever bite living things in self-defence. Their bodies are so hard that when attacked, they roll into a ball and can survive being stomped on, being struck with swords, and being thrown around.