The Mantle of Immortality was a unique magical item which existed from the Beginning, created by the Supreme Master. It could only be bestowed upon a mortal, by a unanimous vote of every immortal.
Since the beginning of time, it was suspended midway between earth and sky, within a high dome in a gleaming crypt of gold and platinum, aglow with the soft light of countless gems.
At the end of his life, it was bestowed upon Santa Claus by the Council of Immortals at the behest of Ak the Master Woodsman. They took it to his house in the Laughing Valley and dropped it upon him. The Mantle closed about him, sank into the lines of his body, and disappeared from view, becoming an inseparable part of his being. (The Life and Adventures of Santa Claus)