The Wolf Fenrir
The wolf Fenrir was the son of Loki (the trickster god).
Fenrir was brought to Asgard, but as he grew he became so fierce that only the god Tyr dared to approach him to feed him.
On one occasion, the gods bound and muzzled him, having tricked him for that purpose using two chains called Læðingr and Drómi, telling him that he would not be able to break free. However, Fenrir managed to do so with ease. They then resolved to bind him with a magical fetter from which he could not escape: he would remain bound until the final battle of Ragnarök.