In order to discover the secrets of runic wisdom, Odin sacrificed himself at the World-tree. For nine days, he hung from Yggdrasill, pierced by his own spear: “pledged to Odin, offered, myself to myself.”

Nine was a significant number in Norse mythology (there were, for example, nine realms of existence) and so Odin learns nine lays of power and the magic of eighteen runes.