How did Odin sacrifice to Yggdrasil?
Odin hung himself on the world tree for nine days to learn the knowledge of runes, and sacrificed an eye to Mimir’s Well, beneath one of Yggdrasil’s roots, for wisdom.
How was Yggdrasil said to signal Ragnarok?
It was prophesied that Yggdrasil would signal Ragnarok was beginning by shaking, and the devastation to follow would eventually consume the world tree.
A mythical and mighty ash tree, Yggdrasil gave structure and definition to the cosmos. According to Norse mythology, all Nine Realms of the cosmos either hung from its branches, or else grew from its massive roots. As the source of cosmic structure, Yggdrasil commanded enormous respect. The Norse revered it as the giver and taker of life and order. Yggdrasil’s fate was synonymous with that of the cosmos itself. Prophecy held that Ragnarok would be preceded by the trembling of Yggdrasil, an omen of the chaos to come.
“Yggdrasil” has a complex etymology and mysterious meaning. The word was formed from the Old Norse yggr, meaning “terror,” and drasil, meaning “horse.” When combined, the two words can be translated as “the tree of terror.”
The complexity of the term arises from the fact that Yggr was a name commonly used for Odin—”the Terrible One.” Many scholars believe that the tree’s name referred to Odin, making it “the tree of Odin.” To further complicate matters, the word “horse” was often used to signify a gallows, rather than an animal; a number of scholars have suggested that the former meaning is correct. In this context, “Yggdrasil” really meansthe “gallows of Odin,” a reference to a well-known mythological episode in which Odin hung himself on the tree in exchange for secret knowledge.
The World Tree
Sources of Norse mythology are rife with compelling descriptions of Yggdrasil, making it possible to describe its characteristics in considerable detail. In the Völuspá, a central work of the Poetic Edda, the völva narrator describes the Yggdrasil as an ash:
An ash I know, Yggdrasil its name, With water white is the great tree wet; Thence come the dews that fall in the dales, Green by Urth’s well does it ever grow.
According to the Grímnismál, another poem in the Poetic Edda, Yggdrasil had three main roots, with each heading off in a different direction. Each of these roots was connected to one of the Nine Realms:
Three roots there are that three ways run. ’Neath the ash-tree Yggdrasil; ’Neath the first lives Hel, ’neath the second the frost-giants, ’Neath the last are the lands of men.
Beneath each of Yggdrasil’s three roots was a well or spring. One of these springs, Hvergelmir, contained innumerable serpents led by the monstrous snake Nídhöggr. Another, known as Urdr’s Well, was the home of Urdr and the nones—mysterious female deities said to control the fates of people. The third was Mimir’s Well. Named for its guardian Mimir—a god renowned for wisdom and wit—the well contained knowledge of the world and its ways. It also contained Odin’s eye, which he sacrificed in his pursuit of wisdom.
The Tree of Knowledge
Revered by gods and mortals alike, Yggdrasil occupied a position of enormous importance in Norse cosmology. In the Gylfaginning, Sturluson presents Yggdrasil as the holiest of locations for the gods, a place where wisdom was sought and gained. The gods met in council at the base of the tree each day, and found inspiration under its massive boughs:
’That is at the Ash of Yggdrasill; there the gods must give judgment everyday. …”
"The Ash is greatest of all trees and best: its limbs spread out over all the world and stand above heaven.”
Odin sought the knowledge Yggdrasil possessed, and would go to incredible lengths to claim it. One myth claimed that Odin sacrificed his eye by throwing it into Mimir’s Well. In return, he was granted the wisdom the well contained.
Another myth, told in some detail in the Hávamál of the Poetic Edda, concerned Odin’s acquisition of the knowledge of the runes and his gift of that knowledge to humankind. Runes were pictographic symbols employed by early Germanic peoples as letters, with each rune standing for a sound. These runes were also thought to embody certain cosmic powers. To know a rune was to know its power, and to know such power was to wield it.
Odin acquired knowledge of the runes through a heroic act of self-sacrifice: he hung himself upon Yggdrasil for nine days. During this time, Odin fasted, pierced himself with a spear, and cryptically offered himself to himself:
I ween that I hung on the windy tree, Hung there for nine nights full nine; With the spear I was wounded, and offered I was, To Odin, myself to myself, On the tree that none may know What root beneath it runs. None made me happy with a loaf or horn, And there below I looked; I took up the runes, shrieking I took them, And forthwith back I fell.
After considerable study, Odin learned to decipher the runes and shared his newfound knowledge with others:
Then began I to thrive, and wisdom to get, I grew and well I was; Each word led me on to another word, Each deed to another deed.
Odin’s sufferings for the sake of humanity—as well as his tormented hanging from the tree—closely resembled Christ’s suffering on the cross in Christian thought and iconography. This resemblance may explain why the Germanic peoples (including the Norse) took to Christianity so readily.
Yggdrasil and Ragnarok
According to the prophecies outlined by the volva narrator of the Völuspá, the events of Ragnarok would be preceded by the shaking of Yggdrasil:
Yggdrasil shakes, and shiver on high The ancient limbs, and the giant is loose; To the head of Mim does Othin give heed, But the kinsman of Surt shall slay him soon.
In time, the destruction of the world would consume Yggdrasil as well.
Yggdrasil still thrives in popular culture as the archetypical guardian tree. In fantasy genres, trees modeled after Yggdrasil are often used to symbolize the health of communities and people. Guy Gavriel Kay’s popular Fionavar Tapestry book series features the Summer Tree, a massive oak whose health depends on the periodic sacrifice of martyrs. Naturally, these martyrs hang themselves on the tree, as Odin did in Norse lore.
Yggdrasil has also appeared in Marvel Comics and the Marvel Cinematic Universe. In Thor (2011), Yggdrasil was reimagined as a tree-shaped constellation whose stars represented the Nine Realms of Norse mythology. Alongside this new interpretation of Yggdrasil, the Nine Realms were reimagined as planets located deep in the vacuum of space.