What is who is garm in norse mythology?

Garm is a monstrous hound in Norse mythology. He is associated with the god Tyr and guarded the entrance to the underworld, Gnipa-cave. Garm was believed to be fierce and dangerous, and it was said that he would howl loudly and furiously when he sensed the approach of the end of the world, Ragnarok. At Ragnarok, Garm was destined to face Tyr in a final battle, where both were prophesied to fall in combat.