Hrimthur: the stonemason who doomed Asgard

Hrimthur was a Jotunn stonemason, the son of the great mason Thamur, who completed the Great Walls of Jotunheim and then turned his skill to vengeance against the Aesir. Disguised as a mortal, he rebuilt the walls of Asgard and concealed within them a weakness that would one day deliver the realm to ruin, a secret he passed to Freya and that was finally exploited in Ragnarok.

Son of the great mason#

Hrimthur possessed excellent skill in masonry, inherited from his father Thamur, who was renowned as the greatest stonemason in the world. Yet to his father's dismay, Hrimthur had the heart of a warrior and refused to help raise the walls around Jotunheim. A quarrel between father and son spiraled out of control until Thamur struck him, and Hrimthur ran away. When Thamur was later killed by Thor while searching for his son, Hrimthur returned to Jotunheim and completed his father's masterwork, the Great Walls of Jotunheim.

The walls of Asgard#

His father's work finished, Hrimthur turned his thoughts to vengeance against the Aesir for their crimes against the Giants. Once he had longed to fight Thor, but the tragedy of his father had taught him wisdom and cunning instead. He observed that the walls of Asgard were half built and shoddy, for no Aesir god would stoop to such labor, and so he adopted the guise of an ordinary mortal and made the Aesir an offer. He would build them magnificent new walls, and if he failed to complete them within two turns of the season they would owe him nothing, but if he succeeded he asked only for an audience with the goddess Freya.

Odin agreed, certain the task was impossible and intrigued by the stranger. With the lessons of his father and the aid of a magical stallion that hauled his stones, Hrimthur completed the work, much to the Allfather's frustration.

The hidden weakness#

Odin seemed to honor the wager and sent Freya to meet the mason. To her surprise, Hrimthur wished only to whisper something into her ear. That done, he made his way toward the entrance to Asgard, where Thor waited for him. It was then that Hrimthur understood he had been double crossed, for Odin had learned who he truly was and meant for him to be slain as his father and most of his kind had been. But he did not care, for his plan was complete.

Mimir long suspected that Hrimthur had built some weakness, structural or magical, into the walls of Asgard, and had given the secret to Freya, who bore little love for the Aesir, in readiness for their downfall. During a later voyage through Svartalfheim, Mimir at last asked Freya what the mason had told her. She confirmed that he had embedded a flaw behind the Asgard Realm Tower, but warned that they could not make use of it themselves, for Hrimthur had said that Surtr would know what to do, meaning the weakness was meant to ease the fire giant's entry come Ragnarok. In the end, during Ragnarok, the dwarf Sindri used a special contraption to blast open the flaw in Asgard's walls, allowing the armies of Kratos to pour into the realm and completing Hrimthur's plan at last.