Yggdrasill, known in Old Norse as Mimameidr, was the World Tree, a towering ash that held up the universe. It grew from the corpse of Ymir, who was oldest of all the giants and killed by the sons of the first god. His blood became the saltwater of the oceans; from his bones rose mountains. His flesh turned to earth and his skull was the sky, with his brains for the clouds. Even the maggots on his corpse were repurposed in this cosmic disembowelment. They transformed into dwarves that held up the sky.
And there was war between the Norse gods and the giants pretty much forever after.
In early Norse legend there were said to be nine worlds growing on the world tree. The realm of mortals was called Midgard. Ygdrasill had three vast roots, each drawing strength from different waters. One reached into Asgard, home of the gods, where it was tended by the goddesses known as the Norns. They were guardians of Urdarbrunnr, the Well of Fate.
The way between Asgard and Midgard was across the Bifrost, the rainbow bridge. The gods lived on the other side of it within a fortress that was built on trickery, broken oaths and murder. The builder of its colossal walls was promised as payment the sun, the moon and the beautiful goddess Freyja, if he could finish his work by the end of a single winter – but when he came too near to earning the gods’ treasures, the gods (well, specifically Loki) sabotaged him so that they would not have to pay up. The builder revealed himself to be a very angry giant, upon which discovery the gods felt their oaths were null and void and Thor smashed his head open.
Within Asgard was the hall of Valhalla, where fallen heroes went to feast in the company of Odin. They ate the meat of the boar Schrimnir, who returned to life each day only to be killed and eaten again, and drank mead milked from the goat Heidrum, who fed on the leaves of Yggdrasill.
The second of Yggdrasill’s roots led to Jotunheim, realm of the giants, and it was watered by the well Mimisbrunnr, a source of wisdom so powerful that Odin gave up an eye to drink from it. In Jotunheim was the city of Utgard, ruled by Utgardloki, a king of giants. He once tricked Thor, Loki and their friend Thialfi into a series of impossible tasks. Thialfi was set against a giant called Hugi in a foot race, but was really trying and failing to outrun Thought itself. Loki was equally unlucky in his eating contest against Logi, who was Fire. Thor was asked to drain a horn that was full of the world’s oceans, to lift a cat that was in fact Jormungand the World Serpent, and wrestle an old woman who was Old Age, implacable even to gods.
It’s fun little get-togethers like this, by the way, that lead howling battles and a lot of dead giants and all the way to Ragnarok, that being the end of the world. Thank you, performative masculinity.
The third root of Yggdrasill plunged into the dark and cold underworld of Niflheim, where it drew water from the well of Hvergelmir but was constantly gnawed upon by the serpent Nidhogge. The Kingfisher Book of Mythology calls it an ‘evil dragon-monster’ but I feel that’s unnecessarily judgy, just because Nidhogge liked to snack on dead people too. Niflheim was one of the first places to ever exist, the other being its counterbalance, the raging fires of Muspell. The land of the dead could be found in Niflheim, ruled over by Loki’s daughter Hel, as could Nastrond, the shore of corpses. Which, incidentally, is where Nidhogge liked to hang out.
The four winds ran across Yggrasill’s branches in the shape of deer, feeding off its buds, and a squirrel darted along the trunk, passing insults from the eagle that lived in the uppermost branches to the serpent at its roots, then back again. I cannot find an origin for that feud but I would really love to know more. Meanwhile, beneath the roots of the universe lay Ymir, shifting uneasily in his death from time to time, causing the tree and the worlds it carried to sway.
Yggdrasill survived Ragnarok. What, though, might happen if Ymir ever woke up all the way?
These stories vary wildly depending on time and teller. If you know an alternative version, I would love to hear it!
References: https://www.britannica.com/topic/Yggdrasill, Mythology: Myths, Legends, & Fantasies – [chief consultant] Dr. Alice Mills (Hodder, 2003), The Kingfisher Book of Mythology: Gods, Goddesses and Heroes from around the World – ed. Cynthia O’Neill, Peter Casterton and Catherin Headlam (Kingfisher Publications, 1998), Bulfinch’s Mythology – Thomas Bulfinch (Gramercy Books, 2003)