Koschei the Deathless

A fearsome villain, an immortal sorcerer who cannot be killed by normal means because his soul (or "death") is hidden outside his body. He is gaunt, with flashing eyes. To defeat him, the hero must find where Koschei hid his soul – usually inside a needle, that is inside an egg, inside a duck, inside a hare, inside a chest buried under a magical oak.