Koschei the Deathless

Origin
Koschei the Deathless was an immortal wizard and evil Tsar, who lived in a gloomy castle. He was said to be a giant, and was often depicted as a boney old man (his name implies that he is boney). In addition to being almost impossible to kill, he was capable of feats of sorcery, including the ability to fly at great speed. He also rode very fast magical talking horses which he obtained from Baba Yaga.

Although he appeared in a variety of Russian fairy tales, he is best known for abducting the warrior queen, Marya Morevna and being defeated by her love, Ivan Tsarevitch.

Koschei cannot be killed by conventional means targeting his body. 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 an iron chest (sometimes the chest is crystal and/or gold), which is buried under a green oak tree, which is 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 (in some tales, this must be done by specifically breaking it against Koschei's forehead), Koschei will die.