One morning, Thor awoke to find his hammer, Mjollnir (“Lightning”), missing. This was no small matter; without the thunder god’s best weapon, Asgard was left vulnerable to the attacks of the giants. In a rage, he searched everywhere for his most prized possession, but it was nowhere to be found.
The goddess Freya owned falcon feathers, with which one could change one’s shape into that of a falcon. She lent these to Thor and Loki so that the hammer could be located. Loki, who knew how to shift his shape, donned the feathers and flew off in search of the treasure. He quickly surmised that it had probably been stolen by the giants, so he rode the winds to their homeland, Jotunheim.
Upon his arrival, he changed back into his god-form and approached the chief of the giants, Thrym (“Noisy”). When questioned regarding the hammer, Thrym answered that he had indeed taken it, and that it was buried eight miles below the ground. And, added the lonely, ugly giant, he had no intention of returning it until Freya was made to be his bride.
Loki flew back to Asgard and told this news to his fellow gods, who were alarmed and furious – especially Freya. As they sat in counsel, Heimdall put forth the following solution: that Thor go to Jotunheim disguised as Freya, and thereby win back his hammer and take vengeance on its thieves. Thor protested, saying that this was a dishonorable and unmanly thing to do, and that all of the inhabitants of Asgard would mock him for it for the rest of his days. Loki pointed out, however, that if he didn’t consent to Heimdall’s plan, Asgard would be ruled by the giants. The gods thereby obtained Thor’s acquiescence.
No detail was spared in the assemblage of Thor’s bridal dress. After the humiliated god had donned the costume, Loki offered to go with him as his maid-servant.
The pair climbed into Thor’s goat-drawn chariot and made their way to Jotunheim. When they arrived, they were welcomed by the Thrym, who boasted that the gods had at last brought him the prize he was due.
At dinner, Thor and Loki found themselves in trouble. Thor singlehandedly ate an entire ox, eight salmon, and all of the dainties that had been prepared for the women – not to mention the many barrels of mead he drank. This made Thrym suspicious, and he declared that he had never in his whole life seen a woman with such an appetite. Loki quickly devised a response: “The fair goddess has been so lovesick for you,” he claimed, “that she hasn’t been able to eat for a week.” Thrym accepted this answer, and was overcome by a desire to kiss his bride. When he peeled back the veil, Thor’s eyes glared at him so intently that they seemed to burn holes right through him. He exclaimed, “Never have I seen a maiden with such frightfully piercing eyes!” Loki, the master of deceit, explained to the giant that while Freya had been unable to eat, she had also been unable to sleep, so fierce was her longing for him.
The ceremony soon followed. As was customary, Thrym called for the hammer to hallow their union. When Mjollnir was laid in Thor’s lap, he grabbed its handle and slew first Thrym, then all of the guests before contentedly returning to Asgard and changing back into his preferred clothes.
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 Simek, Rudolf. 1993. Dictionary of Northern Mythology. Translated by Angela Hall. p. 219-220.
 Ibid. p. 330.
 The Poetic Edda. Þrymskviða.