A hound that guards Hel and prevents the dead from leaving and the living from entering. Garm is chained up at the cave Gnipahellir. Garm and Tyr will kill each other at Ragnarok.

The hound that guards the gate of Hel, queen of death

In Norse mythology, Garm is a huge dog which guards Hel, the land of the dead, alongside of Hræsvelgr and living in a cave called Gnipahellir. Garm was the greatest of all dogs (excluding the Fenris Wolf). During Ragnarök, Garm and Týr will kill each other.

a big as a calf and can breath a fire