Helm of Dominion

This helmet is always worn by the current Lich King or Queen. When he dies the helm instantly teleports to the one who killed him, and this person is now the new Lich King or Queen. The helm CANNOT be taken off.

The soul of the previous Lich King gets trapped in the helmet, and he can thus not be resurrected or raised, not even by a wish.

The helmet is completely indestructible, no known loop holes, nor any known loop holes for freeing the souls stored within.