Nidhogg (Old Norse: Níðhǫggr, [ˈniːðˌhɔɡːz̠]; older Icelandic: Níðhöggr, Modern Icelandic: Níðhöggur) is a Germanic dragon in Norse mythology who is said to gnaw at the roots of the world tree, Yggdrasil, and is likewise associated with the dead in Hel and Niflheim.