Nidhogg

Nidhogg was a giant worm that resided near the Hvergelmir or "Roaring Kettle", one of three sacred wells. Nidhogg constantly gnawed at one of the roots of Yggdrasill ("World Tree") that supported the world, Niflheim.

One of the signs that Ragnarök would arrive would be when Nidhogg finally chewed its way through one of the roots of Yggdrasill.

In the Voluspa (Poetic Edda), Nidhogg was a dragon with wings. He would fly over the plain, carrying corpses. The great serpent enjoyed sucking on the bodies of the dead.