Yggdrasil is the giant ash tree that represents the universe and connects the nine worlds, from the realm of the gods to the lands of men and giants and down to realm of the dead.
In the highest part of its branches is Asgard, the kingdom of the gods, and in the depths of its roots lies Helheim, Land of the dead ruled over by the goddess Hel. In the middle of Yggdrasil is the realm of man called Midgard.
The other six worlds include Vanaheim, original home of the Vanir; Svartalfheim, home of the dwarves; Alfheim, land of the elves; Jotunheim, land of the giants; Muspelheim, a realm of fire; Niflheim a realm of snow and ice.
There are creatures that live on Yggdrasil including the squirrel Ratatosk that carries gossip and malicious messages up and down the trunk between an unnamed eagle that sits at the top of Yggdrasil and the dragon Nidhogg that gnaws on the roots of Yggdrasil. Between the eyes of the eagle sits a hawk called Vedrfolnir. Four wild stags called Dain, Dvalin, Duneyr and Durathror move about in the branches of the World Tree eating its foliage.
Amongst the Great Tree’s roots live the Norns. Wise women that carve runes into the trunk of Yggdrasil weaving the fate of all creatures in the nine worlds.
The World Tree will shake violently during Ragnarok, the twilight of the gods, and afterward a new world will rise from the ocean evergreen, ruled over by a son of Odin named Balder. During the Ragnarok two humans, Lif and Lifthrasir will take refuge in the trunk of the World Tree and survive to see the reborn world.