Garm's History
I know I really made the wrong call on this one - I saw a chained-up wolf in bad shape. I thought, maybe if I freed this guy he'd be happier, or maybe even a friend. How could I possibly know it would tear open realms and wreak absolute havoc? I know he must have been hurting bad, and animals are dangerous when they're hurting... but I wish he'd have let me help him. Now I don't know what's going to happen to him... or any of us, I guess...
-Atreus
Prior to God Of War Ragnarök
Centuries ago, Garm was just a small puppy at the time, but soon began eating parts of Midgard, including a few mountain ranges and the season that comes after Winter, but before spring. Seeing the threat in Garm, the Norse God of War, Tyr, proceeded to lure the monstrous wolf to a safer place. While he let Garm chew on his arm, which was merely a distraction, he had him chained in the process. Once the gates to Helheim were opened, Garm realized that he had been led into a trap, and in rage, he proceeded to viciously rip off Tyr's arm as revenge though this proved only a temporary inconvenience as the god was eventually able to regrow the lost limb.
God of War Ragnarök
Garm is found in Helheim by Atreus and Thrúd while they were searching for the last piece of Odin's mask. Seeing that the giant wolf was in chains, Atreus wanted to free him, but Thrúd tried persuaded him not to as she believed he was in those chains for a good reason. Because they were trying to get behind him, they had to unlock some of the chains holding onto Garm, inadvertantly waking him up. Since some of his chains were unlocked, the giant wolf easily freed himself. When Atreus and Thrud entered the chamber that he was guarding, they found only nothing. When Thrúd realized that all they went through has been really all for nothing, she began to distrust Atreus, as she knew that Odin would get angry at her for setting Garm free.
Thrúd's concerns would be proven valid as Heimdall scolded Atreus for setting Garm free, revealing that it can scratch rifts from one realm to another, and this will allow Hel-Walkers to get through to the other realms. Heimdall's claims proved true as when Atreus later returns to Sindri's house, he found it being attacked by Hel-Walkers who had gone through rifts created by Garm. After a long and hard fight, all the Hel-Walkers involved in the attack were killed and Freya and Atreus were able to seal the rifts with their magic. Though Kratos tells his son that it is not his fault and that it was an accident, Atreus, in shame and guilt, insists that it was his fault for the attack. When he tells his father that he had set Garm free, Mimir was horrified while a despondent Týr states to Atreus that freeing the giant wolf was madness. Moreover, Freya warns the latter that Garm will chew through the fabric of the realms now that he was free and she scolds Atreus for his reckless actions. Kratos proceeded to protect his son and insists the others that Atreus has made a mistake and tells the latter that they'll fix the mistake together. The two then returned to Helheim to stop Garm from doing any more damage.
Initially, Atreus thought he could tame Garm the same way he could take any other wolf, but after their initial plan to re-chain the wolf failed Kratos insisted to his son that he not use any tricks that Odin taught him while he was in Asgard, and that they would have to stop the beast by killing it.
Using the chains that once bound Garm, Kratos and Atreus succeeded in strangling the wolf, leading them to believe that they had succeeded in killing him, but as they tried to leave, Garm was somehow revived, and the beast shot a blast of ice at them. Confronting the hellhound again the pair tried to subdue it again but found that no matter how many times they killed it the beast kept resurrecting, Atreus then noticed that it was as if Garm had no soul, which gave him an idea. Kratos helped his son get onto Garm’s back, using the chains on the Blades of Chaos to boost Atreus onto the giant wolf's head. Remembering what Angrboda had taught him about souls, and how he transferred the soul of a giant into the carcass of a dead snake, he planted his knife, which he realized contained the soul of his pet wolf Fenrir, into Garm’s head, causing it to run off in pain.
Atreus and Kratos were forced to pursue him. As they tracked the giant wolf down, they found his binding cuffs scattered across Helheim. Upon finally catching up to Garm, they found him whining and hiding in a cave. Atreus tried to reassure him, but the beast only growled at him. It was only when Atreus noticed the color of the wolf's eyes and asked the beast if he really was Fenrir that the giant wolf was able to recognize Atreus. Shortly after the revelation that Fenrir's soul was able to take over Garm's body, the beasts body changed into that of Fenrir's, with the fur turning grey & white, and the eyes becoming orange in color, ending the threat of Garm for good.
