from Slavic folklore: Koschei the Deathless, also known as Koschei the Immortal, is most frequently represented as a very old and ugly-looking man. He can’t be killed by conventional means - his soul is hidden separate from his body inside a needle, which is in an egg, which is in a duck, which is in a hare, which is in a chest buried under a green oak tree on the island of Buyan, in the ocean. As long as his soul is safe, he cannot die. If the chest is dug up and opened, the hare will bolt away. If it is killed, the duck will emerge and try to fly off. Anyone possessing the egg has Koschei in their power. He begins to weaken, becomes sick and immediately loses the use of his magic. If the egg is tossed about, he likewise is flung around against his will. If the egg or needle is broken, Koschei will die.
http://en.wikipedia.org/wiki/Koschei
