“I know that I hung on a windy tree nine long nights, wounded with a spear, dedicated to Odin, myself to myself, on that tree of which no man knows from where its roots run.” The Poetic Edda, Hávamál (Sayings of the High One), 138 According to Norse Mythology, Odin performed a self-sacrifice, hanging for nine nights on the World Tree Yggdrasil, pierced by a spear, to gain knowledge of the runes. Each night corresponds to one of Nine Worlds. Each world reviled its wisdom and secrets to Odin.