Hrimthur was the unnamed builder who offered to build a fortification for the Æsir gods that would keep out invaders in exchange for Freyja, the sun, and the moon. After some debate, the gods agreed to this but placed a number of restrictions on the builder, including that he complete the work within one season. When the Æsir realized that the builder was a jötunn, they disregarded their previous oaths with the builder and called for Thor who quickly arrived and killed the builder with Mjöllnir.