Yggdrasil is the sacred tree that holds the universe together. Unlike most of the universe, it has not been fashioned from the remnants of Ymir by Odin and his brothers. Its age and origins are therefore unknown. We should note, however, that Yggdrasil is an ash tree, just like the one from which Ask was fashioned. This combination of events explains the religious significance of ash trees in ancient Norse paganism, which considers this specific type of tree to be sacred.
The sources of Yggdrasil’s power
The Yggdrasil tree draws power from three special sources of water. These sources contain wisdom, poison, and the very fabric of fate itself. One root gets its water from the Well of Fate (Urdarsbrunnr), a holy place near Asgard. This is where the most famous Norns (Urd, Verdandi, and Skuld) spin the fate of all beings. The second root gets its water from Hvergelmir, the maelstrom that is located in Niflheim. This is the starting point for all of Niflheim’s rivers and contains both poison and ice. But how did the water get there in the first place? A giant stag in Valhalla, called Eikthyrnir, gnaws on the branches of the Yggdrasil tree. This causes sap to pour from the tree onto his antlers, dripping all the way down to Niflheim. The third root gets its sustenance from Mimir’s Well in Jotunheim. This is the well of wisdom, which bestows great knowledge on whoever drinks from its contents. One of Odin’s eyes lies on the bottom of this well, as the god has sacrificed it in exchange for a drink from the well.
The citizens of Yggdrasil
Many different lifeforms live in the tree. Four stags hop from branch to branch to eat Yggdrasil’s leaves. A giant eagle sits on top of the tree and flaps its wings, creating winds throughout all realms in the process. The eagle feuds with Nidhogg, a lindworm that lives among the roots of the tree.
Nidhogg devours all oathbreakers that are sent to Helheim after their deaths, but he also gnaws on the very roots of Yggdrasil. When he is bored, he trades insults with the eagle on top of the tree (probably telling him to stop flapping his damned wings!). In return, the eagle returns insults to Nidhogg (probably telling him to leave his roots the Hell(heim) alone). Since both the eagle and the lindworm are unwilling or incapable seek each other out, they used a messenger to trade these insults. A devious squirrel, named Ratatosk, is their messenger. This little deviant enjoys his role so much that he adds some extra insults to each message he carries.