From Norse mythology. Garm is a hellhound who guards Hel, the realm of the dead. His howling is one of the signs of the impending apocalypse, Ragnarok. Often confused for, or seen as related to, Fenrir, the giant wolf.
Garm is the "boss" of the virtual simulator in Valhalla.
Shin Megami Tensei IMAGINE
"A hunting dog that appears in Germanic mythology. Garm guards Eljudnir, Hel's hall in Niflheim, and is chained in the cave of Gnipahellir. He chases away all who approach the underworld, allowing only Odin to pass. At Ragnarok, he will be released from his chain, and his howl will announce the beginning of the end. After an epic battle with Tyr, the dying Garm will sink his teeth into Tyr's throat, sending both to their deaths. Although he appears vicious at first glance, Garm is actually a big softie, timid and lonely. He is sometimes identified with Fenrir."
—Shin Megami Tensei IMAGINE Compendium
Garm appears as a boss within Suginami Tunnels' bronze instance and its Unknown instance boss rush. It can be contracted on Nakano field. Players are able to obtain its collar, tail, and other equipment drawing from its appearance.
Devil Children Red/Black Book
Garm is a bounty hunter who comes after Setsuna Kai in Black Book after he escapes Ice Land's jail. Upon being defeated he warns that he hasn't seen the last of him, disappearing. Garm confronts Setsuna and Cool again in Sand Land alongside his leader Fenrir, dying after the battle.
DemiKids Light & Dark
"With eyes like burning coal, this relentless hunter never rests until it nails it prey."
Known as Garum, he can perform the Fire Combo Evil Blaze with Krane, which deals fire damage and inflicts bomb on all foes.
Devil Children Messiah Riser
S-Ranked Garms can be obtained from story battles in Ice Makai on Akira's route.
Devil Survivor 2
"The hound of Hel, queen of the underworld. It watches the entrance to Niflheim, kingdom of the decreased. The black fur on its chest is tainted scarlet from the blood of the dead. Its four eyes burn like coal, with which it keeps watch over the decreased and mercilessly mauls those who attempt to escape. Though it is bound by an unbreakable chain, it will be released during Ragnarok to duel Tyr. The two of them will slay each other."