I'm not sure about Demonesses, however i can confirm that Dryads charmed units can be sacrificed. But as this has a fairly low trigger rate, Druids animal charm is much better as it always works! Just wait until after the animal takes it's turn if you are a warrior, use the Druids charm then immediately cast Sacrifice. Next turn use your dragons mana ball and cast again. If you still have enough mana, you can actually get 3 Sacrifices b4 the 2 turn charm wears off.
