In Norse mythology, which dragon was known for gnawing at the roots of Yggdrasil, the tree which supports the nine worlds of Norse mythology?

Nidhogg or Níðhöggr in the Norse pronunciation; is considered to be a ferocious dragon who gnaws at the roots of Yggdrasil, the tree which supports the nine worlds of Norse mythology. This dragon is considered to be a power-hungry monster who is sometimes referred to as “the Malice Striker,” an appropriate name given that he rules over dark criminals and is bent on destroying peace and virtue.

In the Norse mythology Nidhogg is the dragon that is always battling with the Eagle at the upper branches that represents good. This constant battle in the mythology represents the constant battle between good and evil, with the renewal of life and healing that comes from the after battle between these two creatures.