Yggdrasil the world tree is rooted deeply in Norse mythology. This gigantic ash tree reaches the nine worlds with its branches, and in addition to being where the gods hold their daily court, Yggdrasil is home to several other mythological creatures. Nidhogg the great dragon dwells below gnawing on the roots of Yggdrasil, while Ratatoskr the messenger squirrel runs up and down its trunk, and up in the highest branches there is an unnamed eagle with the hawk Vedrfolnir sitting on his head.
One of the most well known tales about Yggdrasil features the all father Odin hanging himself upon the world tree as a sacrifice unto himself. Wounded by his own spear and without food or drink for nine days Odin was bound to the tree. He endured this suffering for the sake of gaining great wisdom, until finally the runes and their magic were revealed to him.