Garm is associated with the end times prophecy in Norse mythology. Ancient influences of the hellhound Cerberus may have played a role.
Garm is the hound of the goddess of the dead Hel, ruler of the underworld and guards the entrance to the underworld at the dead river Gjöll, dwelling in the cave Gnipahellir. He charges at anyone who approaches the underworld. Odin meets him on his ride to Helheim.
On the day of the end of the world (Ragnarok) Garm will tear himself away with a terrible howl and fight at the side of the giants against the Aesir. In the duel with Tyr both will find death.
In the Grímnismál, an early oral song of the gods from the Icelandic Song-Edda written down in the 13th century, Garm is described in stanza 44 as the "best of all dogs."
In Baldrs draumar, another part of the Song-Edda, Odin, on his way to the underworld in Helheim, encounters a bloodied dog that follows him barking for a long time.
In the Gylfaginning, the central part of the Snorra-Edda, Snorri Sturluson calls Garm "the greatest monster" and informs in his detailed description at the end of the world Ragnarok that Garm, who has broken free from his fetters in front of the cave Gnipahellir, fights with the last Aesir Tyr and both meet their death.
In the 13th century poem Fjölsvinnsmál, the beautiful castle of Menglod is guarded by dogs, which are also referred to by the term Garm. In other poems it is described that Garm can only be pacified with a piece of bread from someone who has already given bread to a poor person.
The concept of a hound guarding the underworld or the realm of the dead is also known in other mythologies. In Greek mythology there are several dogs or dog-like mythical creatures with proper names. Corresponding to the Norse Garm is Kerberos (also Cerberus), a two- or more-headed dog with a dragon or snake tail that guards the gates to the underworld and only allows the souls of the dead to enter, but never to leave.
In a Greenland Inuit legend, after an unsuccessful seal hunt, an angakok dives to the sea goddess Sedna at the bottom of the ocean to ask her to release the seals. On the way to her, first the realm of the dead must be crossed, followed by an abyss guarded by a large dog, and finally another abyss, crossed by a bridge as narrow as a knife blade.
Slavic mythology knows Zorya or Zarya, the goddesses of the dawn. The dawn of the morning opens the gate for the sun for its daily migration across the sky, that of the dusk closes it again after its return in the evening. In a late version of the myth, another zorya, that of the midnight, was added. These three sisters had the task of guarding a dog chained to the constellation of the Little Bear so that it would not break loose, otherwise the end of the world would be imminent.