This is Mylles and the Yggdrasil Key. Yggdrasil is the Immortal World, from which he comes. And the key he holds opens the gates to Yggdrasil. Mylles' jobs are to protect mortals and immortals, guard the gates to Yggdrasil, and make sure everything is okay in the mortal world. He also has a Divine Guardian name: The Guardian of Life and Death. Another thing he's known as is 'The Balance Keeper' because he keeps the balance between the living and the dead in order. Whew!