In gaming terms, I guess we could think about it as Fire Rats, maybe.
Or maybe Magma Rats. They eat coal and poop cinders. The have been known to infest steam-powered machinery to get to the yummy, yummy coal. Plus, the machinery keeps the poor dears warm, sometimes destroying it in the process. As a result, Dwarves hate them, and their legendary grudge against these beasts explains the sheer number of dwarven ratcatchers in the Warhammer Fantasy RPG world.