Sneaky bastards, the lot of them
Some sovereigns prefer a different sort of tax from their subjects - whether freely given, or taken by force.
A dreamer is one who can only find his way by moonlight, and his punishment is that he sees the dawn before the rest of the world
The spellbook of a long dead wizard that has gained the ability to read itself and cast spells from itself. If could be amazingly powerful as an ally, or use its magic to manipulate and rule a kingdom.