Who Chews on the root to Niflheim In Norse mythology?

In Norse mythology, the dragon Nidhogg chews on the roots of Yggdrasil, the world tree, which is connected to Niflheim, the realm of ice and mist. Nidhogg's gnawing symbolizes decay and the destructive forces that threaten the cosmos. This act highlights the interconnectedness of the realms and the constant struggle between creation and destruction in Norse belief.