In Norse mythology, the world tree .
One of its roots extended into the underworld, another into the land of the giants, and the third into Asgard . At its base were three wells: the Well of Fate, from which the tree was watered by the Fates; the Roaring Kettle, in which dwelt Nidhogg, the monster that gnawed the tree's roots; and Mimir's Well, the source of wisdom, for whose water Odin sacrificed an eye. After the Ragnarok , Yggdrasill, though badly shaken, is to be the source of new life.