Mjölnir is the hammer of Thor, the Aesir god associated with thunder. Mjölnir is depicted in Norse mythology as one of the most fearsome and powerful weapons in existence, capable of leveling mountains. In its account of Norse mythology, the Prose Edda relates how the hammer's characteristically short handle was due to a mistake during its manufacture. The mistake was caused by Loki, under the guise of a fly, biting Brokkr on the eyelid during the hammers creation, which caused the dwarf to briefly stop working the bellows of the forge in order to wipe the blood out of his eye, which caused the hammer to not come out perfect and therefore wouldn't be as good as the other gifts he commissioned for the Aesir from the Sons of Ivaldi. Loki did this in an effort to win the wager he made with Brokkr and Sindri that stated they could take his head if their gifts were deemed better than Sons of Ivaldi's by the other Gods, but if they weren't they would leave with nothing.
The weapon was forged by the Huldra Brothers Brok and Sindri, back when they were relatively unknown blacksmiths, eager to make a name for themselves. Presenting the hammer to Thor, it quickly became the deadliest and favourite weapon of the Aesir, ensuring their dominance and allowing the Thunder God to massacre scores of Jötnar with devastating ease.
After seeing the destruction wrought on giants with the very weapon they created, the two brothers suffered a profound sense of guilt. As a way to try and make up for their mistake, they then forged the Leviathan axe, a weapon capable of rivaling even Mjölnir and gave it to the last guardian of the giants left in Midgard; Laufey.
The hammer is extremely powerful, capable of killing most beings with one hit and channeling a vast amount of electricity.
- Noted as the hammer's only flaw, the handle was made too short due to a fly (Loki) biting Brok on one of his eyes during the forging of the hammer.
- Despite possibly being the greatest weapon in all of the Nine Realms, only rivalled by the Leviathan and Surtr's sword, Odin is capable of making certain things indestructible even by it, as according to Mimir the tree he is imprisoned in cannot be destroyed even by Mjölnir.
- In Norse mythology, Thor has a pair of magic gauntlets and a belt that he always wore when wielding the hammer. The belt, named Megingjörð ("power-belt"), doubled Thor's already divine strength which allowed him to use Mjölnir to even greater efficiency. The gauntlets were named Járngreipr ("iron grippers").
- Járngreipr and Megingjörð were not actually required to be worn in order for Thor to wield the hammer, contrary to popular belief, as has been noted to be able to wield it effectively without them. The most prominent example of this being when he slaughtered the Jotunn Þrymr and his kin while disguised as a bride.
- Though Brok and Sindri express guilt for all the destruction brought about by Thor's use of their hammer, they still acknowledge it as their greatest work, albeit bitterly.
- The hammer appeared before in God of War: Ascension's Multiplayer as an add-on and possible nod to the future of the franchise. This, however, is the Canon version of the hammer.
- In Norse mythology, Magni and Modi were said to have inherited the hammer together, as it was so heavy it required both of them to wield it effectively. This does not appear to be the case in God of War, however, as they are in open competition for the hammer and both Magni and Modi were killed by Kratos and his son Atreus, leaving Thor's daughter Thrud as the only possible inheritor.
- Contrary to popular depiction/belief; Mjolnir is not the source of Thor's lightning. That power is innate within in him as a storm/thunder God. The hammer is merely a weapon built to withstand the God himself as he was infamous for breaking and/or losing all other weapons that were forged for him. The Prose Edda describes the hammer as being unbreakable so it would never fail under Thor's immense strength, never missing the target it was thrown at, always returning to Thor's hand no matter how far he threw it and being of a convenient size so it was easy to carry around. There is no mention of the weapon being the origin of the Thunder God's lightning.
- Interestingly in Norse Mythology, it is implied that there are those among the Jötnar having the strength required to lift the hammer, including Loki. When Thor first awakens to find his hammer stolen, his first instinct is to blame the trickster, only to then realise that even Loki would not dare do something so foolish as to steal his hammer. Note; the Thunder God did not dismiss the notion on account of Loki's physical strength. The same story also shows that Þrymr the King of the Jotnar is able to lift it, as he can steal it from Thor and also later placed it on lap of "Freya" (Thor in disguise).
- This has an interesting implication that Thor's great strength that allows him to wield the great hammer in such effective manner comes from his Jötnar's heritage.
- When Kratos and Atreus reach the Corpse of Thamur, Mimir remarks in regards a particularly thick wall of ice, that even Thor with Mjolnir in hand could not get through it. However, it is highly likely that this was an exaggeration, as Thor has been noted both in-game and in the Lost Pages of Norse Mythology podcasts to be immensely powerful and can easily shatter a Jotunn skull with a single throw of the hammer. Considering Thamur, who himself was defeated by Thor (though to be fair, Thor really just got lucky, since Thamur really slipped), is many times larger than the wall of ice in question, it also casts further doubt on Mimir's claim that a mere wall of ice would hinder the God of Thunder and Strength.
- Ironically, in Norse Mythology, Loki himself is responsible for inspiring Sindri and Brok to forge Mjolnir. According to the Prose Edda, Loki pulled a prank on Thor's wife, Sif, by cutting all of her hair off while she was sleeping. Thor was not amused and threatened to break every bone in his body. To avoid this, Loki convinced Thor to let him go by promising to find him master craftsmen to replace Sif's hair. Loki planned to start a challenge between the Sons of Ivaldi and Brok and Sindri, by feeding them lies about each other. Brok and Sindri, however, were not fooled, and made a wager; if they won, Loki would have to forfeit his head. The trickster tried to sabotage them, which he did in the form of causing the Mjolnir's handle to come out shorter than intended, but the other Gods (Thor especially) still decided it was the overall better gift when both groups of Dwarves presented their respective gifts. Brok and Sindri won the challenge, but Loki found a loophole, stating that his head was to be forfeited, but not his neck and thus the dwarves had no right to cut it, to which the other Gods agreed. Brok, having been cheated of the chance to take Loki's head due to the ambiguous nature of where the neck truly ended and the head began, found an alternative by sewing Loki's mouth shut, as revenge for his craftiness.
- Interestingly the head of the hammer on the statue of Thor is upside down compared to the what Thor is holding at the end cut scene.