Yggdrasil, also known as the World Tree or The Great Ash, upholds the Nine Realms and is a prominent part of Norse Cosmology. Yggdrasil has three main roots which each connect to one of the three planes that support the Nine Realms. One of Yggdrasil’s roots is located in Nifelheim, the realm of the dead. Above this root is the Well of Hvergelmir, the source of the eleven rivers that run through Nifelheim. Located beneath the roots of Yggdrasil is the dragon Nidhogg which continuously devours the corpses of the dead and gnaws on Yggdrasil itself.The second root stretches toward Asgard, the realm of the gods and to the Well of Urd, the waters associated with Fate and the Norns. The Norns themselves are important in Norse mythology and are powerful female spirits who guard the Well of Urd, carving the runes foretelling the future and destinies of mortals and gods into Yggdrasil. The Norns also care for Yggdrasil, sprinkling the tree with waters from the Well of Urd to sustain the tree.Yggdrasil’s third root is located in Jotunheim, the realm of the frost giants. Beneath the third root is the Well of Mimir, guarded by Mimir, the wisest figure in Norse myth but of uncertain origin. Although Mimir was beheaded during the war between the Aesir and Vanir, Odin takes Mimir’s head and magically embalms it, preserving the ability for Mimir to speak and offer his wisdom. Uncertainty continues whether Mimir was a god or a giant but the location of the Well of Mimir in Jotunheim is as intriguing as the legendary waters giving wisdom to all who drink from it. Despite Yggdrasil’s obvious importance in Norse cosmology, the tree is vulnerable. Constantly afflicted by the magical creatures dwelling upon it, the Norns tend Yggdrasil but the dragon Nidhogg gnaws at the root in Niflheim, the stags and goats eat the leaves and new shoots in the upper branches but Yggdrasil endures, surviving even after the un-making of the cosmos during Ragnarok.