The tale of Hrungnir is documented in the second part of the Prose Edda, Skáldskaparmál.
Hrungnir engaged in a wager with Odin in which Odin stakes his head on his horse, Sleipnir, being faster than Hrungnir's steed Gullfaxi. During the race, which Sleipnir wins, Hrungnir enters Valhalla, and there becomes drunk and abusive. After they grow weary of him, the Gods call on Thor to battle Hrungnir.
Hrungnir hurles a flint-stone towards Thor, who in turn hurles Mjölnir, shattering both the whetstone weapon and Hrungnir's skull. After his death, the Jötunn's steed Gullfaxi was given to Thor's son Magni as a gift for releasing his father from Hrungnir's corpse.
Hrungnir was born with neither head nor heart, so his people had to complete his body with stone, thus he grew into a complete simpleton.
One day he was wandering the realm of Midgard when Odin crossed paths with him. The King of the Aesir was so amused by the stone giant's gullible nature that he invited him to his hall in Asgard to amuse his court.
After having his fill of mead, a drunken Hrungnir became rowdy and begun to threaten the Aesir, which the Aesir simply took as a joke. Then Thor arrived, took one look at Hrungnir, and decided that he was not amused. Thor then struck the giant in the head with Mjolnir so hard that chunks of Hrungnir became buried in Thor's own skull.
The thunder god was so startled by the faceful of rock, he was unprepared as Hrungnir's gigantic corpse fell right on top of him, much to the amusement of the whole court of Asgard. No one in the court was strong enough to free the thunder god and even Thor himself was unable to remove it, having gotten too drunk to exert enough strength to do, but then little Magni and Modi, no taller than shrubs at the time, entered the hall and effortlessly flipped over the stone giant, freeing their father. Despite both brothers performing the deed together, only Magni received any of the praise for the accomplishment because he simply the more blonder of the duo, which left Modi bitterly jealous due to having been overshadowed by his older brother. Unknown to everyone in the room however, Odin’s advisor, Mimir, was the only one who witnessed both brothers freeing Thor.
Mimir later used his story to teach Atreus that truth is seldom as pretty as myth and legend.
Powers and Abilities
Thanks to having parts of his body made of stone, Hrungnir was an incredibly strong giant. He most likely enjoyed to fight, since he gained the nickname of Hrungnir the Brawler. After his death by Thor, Hrungir's corpse is so heavy when crushing Thor.
- Hrungnir is depicted with a shield in his shrine, a shield that in Norse mythology was made from the same stone that his head and heart were made.