The venom-dragon gnawing the root of the World Tree
The venom-dragon coiled beneath the deepest root of the World Tree Yggdrasil, gnawing at the root day and night, symbol of the death and decay that eat away at all things. It also feeds on the corpses of oath-breakers in the river of the dead. The squirrel Ratatoskr runs up and down the tree, carrying insults between it and the eagle at the treetop — the least dignified messenger among the nine worlds.
Níðhöggr lies beneath a root of the World Tree, gnawing year after year. The tree joins the nine worlds by three great roots — one gnawed by the dragon, one with the well of wisdom, one watered by the goddesses of fate — and the tree’s survival and decay hang in the tug-of-war between this watering and this gnawing. It is said that after the old world’s destruction, Níðhöggr still beats its wings over the newborn earth.
Below are how modern works borrow or reinterpret this name or story — not the original material. The two differ, so keep them apart.