In the beginning of all things, there was Yggdrasil — the World Tree. It was an ash tree so enormous that no one could walk around it in a lifetime, so tall that its highest branches touched the stars, and so deep that its lowest roots reached places where the light had never gone. Its bark was warm to the touch, as though something alive pulsed within. And nestled in its branches and roots, like birds' nests in an ordinary tree, were nine whole worlds.
The creature who knew Yggdrasil best was not a god or a giant. It was a squirrel. Ratatoskr was small and red and extremely pleased with himself. He ran up and down the world tree all day, every day, carrying messages between the great eagle who lived in the crown and the dragon Nidhöggr who gnawed at the roots below. The messages were usually insults. Ratatoskr delivered them with enormous enthusiasm, occasionally adding a few extra insults of his own.
High in Yggdrasil's crown, in the world of Asgard, lived the gods. Golden towers and long halls stood among the tree's highest branches, and from up there the gods could see all the worlds below. Ratatoskr scurried past Odin's hall Valhalla, past the gleaming wall of Asgard, past the rainbow bridge Bifrost that arched down through the branches to the world of humans. He paused just long enough to deliver a particularly rude message from Nidhöggr to the great eagle in the treetop.
The eagle received the insult with magnificent dignity and sent back an even ruder reply. Ratatoskr memorized it carefully, turned, and launched himself down the great trunk, skittering through branches and past leaves as big as houses. Below Asgard, in the middle branches, he passed through Midgard — the world of humans — where the branch-highways were warm and green and smelled of good earth and cooking fires.
In Midgard, people were going about their day: farmers tending fields, smiths hammering iron, children playing games that involved a lot of falling over. None of them could see Yggdrasil with their ordinary eyes — the tree was too vast and too fundamental for human sight. But they all felt it: the ground beneath their feet, the air around them, the sky above — all of it was Yggdrasil. They simply didn't have a name for this feeling.
Ratatoskr descended further, into the wilder middle branches where the frost giants of Jotunheim built their ice-and-stone halls. He darted between enormous feet, ducking under massive hands that occasionally tried to catch him (unsuccessfully). Then he swung east to Vanaheim, where the nature gods tended forests so ancient that the trees had names and personalities. The plants here grew in patterns Ratatoskr had memorized over centuries.
The lower branches were stranger still. In Alfheim, where the light elves lived, everything glittered with a silver-white radiance that made Ratatoskr's red fur look even more magnificently red. The elves moved like blown leaves, always slightly out of focus, dancing in light that seemed to have no source. In Svartalfheim, the world of dwarves and dark elves, the forge-fires burned day and night, and the sound of hammering rang through the roots.
Down near the roots, the temperature dropped. Ratatoskr's breath misted in the air as he entered Niflheim, the world of ice and mist, where ancient glaciers moved with a sound like sleeping whales. The river Elivagar ran through it in slow, cold coils. Above Niflheim — but connected to it by the roots — lay Helheim, the quiet realm of the ordinary dead, where those who had not died in battle rested in gentle grey stillness.
On the other side of the tree's roots, as different from Niflheim as fire from ice, lay Muspelheim — the world of fire. Here the air shimmered with heat and the sky was always orange with flame. The fire giants moved through it like burning ships, and from their realm would come the fire that would eventually light the sky at Ragnarök. Ratatoskr visited only briefly — his fur was getting uncomfortably warm.
And finally, at the very deepest roots, Ratatoskr found what he had been looking for: Nidhöggr, the great dragon, wrapped around the thickest root of all, gnawing at the wood with patient, ancient teeth. The dragon had been doing this since the beginning of time. Nobody was entirely sure why. 'Message from the eagle,' announced Ratatoskr, reading out the very rude reply with professional relish. Nidhöggr opened one enormous eye. Composed a devastating response. Ratatoskr memorized it and turned to run.
Running back up the great tree, Ratatoskr thought about what he knew: nine worlds, all different, all connected by these roots and branches. Asgard above, Midgard in the middle, Niflheim below. Fire and ice. Light and dark. Gods and giants and humans and dragons and dwarves and elves, all of them part of one enormous living thing. He had run this route ten thousand times. He would run it ten thousand more. Not because he had to — but because the tree was interesting.
Ratatoskr delivered his final message to the eagle — who bristled magnificently — and then sat for a moment on a high branch, looking out across the nine worlds. The northern lights played between the worlds like ribbons. Stars shone above Asgard. Fires burned in Muspelheim far below. And the tree pulsed around him, warm and alive, holding everything together as it always had and always would — at least until the last day came. Ratatoskr flicked his tail and ran on.
