Hrungnir

It began with a horse race: Odin on Sleipnir wagered his head against Hrungnir's golden-maned Gullfaxi, won, and rode home with the furious giant galloping into Asgard behind him. The gods, oddly, poured him a drink. Many drinks. Hrungnir boasted he would sink Asgard, kill every god, and carry off Freyja and Sif — at which point the gods named Thor.

The duel was arranged at the borderland with formal rules, the first hólmganga of myth. The giants built a clay decoy nine leagues tall (its heart failed on seeing Thor); Hrungnir stood behind his stone shield until told Thor would attack from below — then stood on the shield, which is why giants lose. Hammer met hurled whetstone in mid-air: the whetstone shattered, a shard lodging forever in Thor's skull; Mjölnir continued to its appointment. The giant's leg fell across the god's neck, and no one could lift it but Magni, Thor's son, aged three. Whetstones tremble, the skalds said, whenever Thor's shard itches.

Hrungnir is the strongest of all the giants in the sources' own estimation — Snorri says the gods knew him as the mightiest of his kind — and his myth is the mythology's meditation on strength itself: what it is worth, what it costs, and what it looks like when two avalanches meet by appointment. It is also, unusually, a story about rules. Gods and giants normally kill each other by ambush, theft, and trickery; Hrungnir and Thor fight the one formal, refereed duel in the mythic record, and both sides keep the forms.

The horse race and the drunken guest

Skáldskaparmál sets the scene with Odin doing what Odin does: riding out on Sleipnir into Jötunheim, looking for trouble and information. Hrungnir admires the stranger's remarkable horse; Odin wagers his own head that no horse in giant-land can match it. Stung, Hrungnir leaps onto Gullfaxi — "Gold-mane" — and the race is on, the giant so hot with rage that he does not notice the finish line until he is inside the gates of Asgard. And here the story takes its telling turn: rather than kill the intruder, the gods observe the guest-law. They invite Hrungnir in and set out drink — Thor's own goblets, as it happens, since Thor is away east killing trolls.

Hrungnir empties every one, and the ale does its work. His boasts swell with each cup: he will pick up Valhalla and carry it to Jötunheim; he will sink Asgard beneath the earth and kill every god in it — except Freyja and Sif, whom he will take home with him. Freyja alone dares keep pouring for him. When the gods weary of his bragging, they name Thor, and the hall fills with the god himself, hammer raised, demanding to know who allowed a giant to drink in Valhalla under Freyja's protection. Hrungnir, meeting Thor's eyes with a drunkard's clarity, points out that he is an unarmed guest: killing him now would win Thor little honor. Braver, he says, would be to meet him at the border, at his homestead Grjótúnagarðar — "Stone-fence-yards" — for he has left his shield and whetstone at home, like a fool. Thor accepts instantly; no one had ever offered him single combat before, and the appointment is struck. Even Loki could not have scripted it better: the giants realize at once that everything rides on the outcome, for if Hrungnir falls, who among them can stand?

The duel at Grjótúnagarðar

The giants' war-preparations are the myth's great grotesque set piece. At Grjótúnagarðar they build a second combatant out of clay, nine leagues tall and three broad under the arms — a decoy colossus called Mökkurkálfi, "Mist-calf." They could find no heart big enough for him except a mare's, "and that proved unsteady in him when Thor came." Hrungnir himself needed no such improvisation: his heart was stone, sharp-cornered and three-pointed — the shape, Snorri notes, of the carved sign afterward called "Hrungnir's heart." His head was stone too, and his shield stone, broad and thick, and he stood behind it at the dueling ground with his whetstone across his shoulder, "and he was not pretty."

Thor came to the hólmganga with his second: Þjálfi, his human servant and the fastest of runners. And it is Þjálfi who wins the duel before it starts, sprinting ahead to tell Hrungnir — helpfully, confidentially — that Thor has seen him and is coming at him underground, from below. Hrungnir promptly stands on his shield and grips the whetstone two-handed, whereupon Thor arrives in thunder and lightning, from precisely the direction gods come from, and throws Mjölnir from a distance. Hrungnir hurls the whetstone to meet it. The weapons collide mid-air: the whetstone bursts, half falling to earth — whence come all whetstone rocks, says Snorri — and half driving into Thor's head, dropping him. Mjölnir, unbothered, continues on and shatters Hrungnir's stone skull. The giant falls forward, one enormous leg across the fallen Thor's neck; Mökkurkálfi, meanwhile, is dismantled by Þjálfi "with little glory," having reportedly wet himself at the sight of Thor.

Then the coda, which the tellers clearly loved: none of the Æsir can lift Hrungnir's leg off Thor. His son Magni — his boy by the giantess Járnsaxa, three years old (Snorri actually says three nights old in some manuscripts' reckoning; the sources revel in his impossible infancy) — tosses the leg aside and remarks that it is a shame he came so late: he would have knocked this giant into Hel with his bare fist. Thor, delighted, gives the boy Gullfaxi, the dead giant's golden-maned horse — and Odin grumbles that so fine a horse should have gone to the boy's grandfather, not to the son of a giantess. The Allfather's pettiness, immortalized.

Why is there a whetstone in Thor's head?

Because it never came out — and thereby hangs the myth's strange tail. The völva Gróa, wife of Aurvandill the Bold, was brought to sing charms over Thor, and the stone began to loosen. Thor, feeling it give, wanted to pay her at once with good news: he had carried her husband home from Jötunheim in a basket, and one of Aurvandill's toes, sticking out, had frozen — so Thor broke it off and threw it into the sky, where it shines as the star called Aurvandill's Toe. Gróa was so overjoyed she forgot every charm she knew, and the whetstone sits in Thor's skull to this day. Hence, Snorri says, the taboo: never throw a whetstone across a floor, for then the stone in Thor's head stirs. It is a perfect Norse etiology — a god's chronic headache explaining a household superstition — and it means Hrungnir, alone of all Thor's victims, wounded him permanently. The skalds used "Hrungnir's skull-splitter" for Mjölnir and built dozens of kennings from the duel; the ninth-century shield-poem Haustlöng devotes half its stanzas to it, with the earth trembling and Thor's chariot-goats splitting the sky as he drives to the meeting.

In the primary sources

Skáldskaparmál in the Prose Edda carries the full narrative — race, feast, duel, Magni, Gróa — told to explain kennings like "Hrungnir's heart" and quoting Haustlöng, by the ninth-century skald Þjóðólfr of Hvinir, which describes the duel as painted on a shield and is among the oldest surviving witnesses to any Thor myth. In the Poetic Edda, Hrungnir's fame is assumed rather than told: Hárbarðsljóð has Thor cite the killing ("I slew Hrungnir, that stout-hearted giant whose head was all of stone") in his boasting-match, and Lokasenna uses "Hrungnir's bane" as a title for the hammer-god. The stone-heart sign and the whetstone taboo hint that the myth once lived in ritual and folk custom as well as verse.