In Norse mythology’s Ragnarok, Níðhöggr is the serpent-dragon that gnaws at the roots of Yggdrasil. He dwells beneath the world tree, associated with the subterranean realm and the corpses of the dishonored dead.
Níðhöggr is not the same creature as Jörmungandr, the Midgard Serpent. Jörmungandr encircles the world and fights Thor at Ragnarok, while Níðhöggr is linked to Yggdrasil’s roots and the underworld. Their dragonlike or serpentine descriptions can cause the names to be mixed up.
The Poetic Edda also depicts Níðhöggr as one of the creatures involved in the tree’s wider ecosystem. After Ragnarok, the dragon is described as flying with corpses, a grim image that reinforces the poem’s themes of decay and cosmic upheaval.