Dragons steal gold and jewels, you know, from men and elves and dwarves, wherever they can find them; and they guard their plunder as long as they live (which is practically forever, unless they are killed), and never enjoy a brass ring of it. Indeed they hardly know a good bit of work from a bad, though they usually have a good notion of the current market value; and they can’t make a thing for themselves, not even mend a little loose scale of their armour.
From chapter one of The Hobbit by Tolkien. (I’m reminded that, when fighting sin, being “weak on dragons” is a real set back.)