Third item in Thor's kit: Járngreipr, "iron grippers," the gauntlets without which even Thor cannot handle Mjölnir's stub of a handle — the flaw Loki's fly-bite left in the forging, compensated in ironmongery. The greatest weapon in the cosmos ships with mandatory safety gear.
Snorri Sturluson lists the gloves in Gylfaginning alongside the hammer and the belt of strength Megingjörð, saying only that Thor may not do without them when he grips the hammer's shaft. It is the mythology's shortest job description, and it makes the gloves the least glamorous of the great treasures: not a weapon, not an ornament, but an interface. Yet in their one starring scene they do something no other artifact in the North ever does — catch fire out of the air and throw it back.
Why does Thor need iron gloves?
The answer runs back to the forging of the hammer itself. In Skáldskaparmál's famous wager, Loki bet his head that the dwarf brothers Brokkr and Sindri could not out-craft the smiths who made Gungnir and Skíðblaðnir. As the iron that would become Mjölnir lay in the forge, Loki became a fly and bit the bellows-hand; the blast faltered for a moment, and the masterpiece came out with a single flaw — a shortened handle. The gods judged the hammer the finest treasure ever made and the best defence against the frost-giants regardless, but the defect stood.
Snorri never draws the line explicitly from short handle to iron gloves; he states the flaw in one chapter and the necessity in another, and readers have connected them for centuries. The connection is natural: whatever forces run through a weapon that strikes as hard as Thor can throw, never misses, and returns to his hand must go somewhere, and the gloves are where. A popular modern notion adds that the returning hammer comes back glowing hot; that detail is nowhere in the sources. What the sources actually give us is stranger and better: the one being strong enough to wield the hammer still needs protective equipment to do it. Power, the myth says, is dangerous first of all to the hand that holds it.
Catching fire in Geirröðr's hall
The gloves' finest hour comes in Skáldskaparmál, in a story where — as with the belt — Thor's own set stays home. Loki, caught in a borrowed falcon-skin and starved by the giant Geirröðr, bought his life by promising to bring Thor to Geirröðr's courts without hammer, belt, or gloves. On the way, the giantess Gríðr — mother of Odin's son Víðarr — warned Thor what he was walking into and lent him her belt of strength, her staff Gríðarvölr, and a pair of iron gloves.
He needed all three. The river Vimur rose in flood against him — Geirröðr's daughter Gjálp was swelling the waters — and Thor braced on the staff and stemmed the torrent. In the giant's guest-house, the seat beneath him surged toward the roof: Gjálp and her sister Greip were under the chair, lifting. Thor drove the staff against the rafters, pushed back, and broke both their backs.
Then came the duel Geirröðr had planned all along. The giant seized a glowing ingot of iron with tongs and hurled it down the hall at his guest. Thor, in borrowed iron gloves, caught the molten bolt out of the air. Geirröðr ducked behind an iron pillar; Thor threw the ingot back, and it passed through the pillar, through Geirröðr, through the wall behind him, and into the earth outside. Catching what your enemy throws and sending it back harder is the entire Thor doctrine, expressed as handwear.
One glove or two — and whose?
The name Járngreipr is a plural: "iron grips," a pair, sometimes given in the variant járnglófar, "iron gloves." That much the texts settle. Ownership in the great story is left delightfully unsettled: Thor's own gloves sit out the Geirröðr adventure by the terms of Loki's bargain, and the gloves that catch the ingot are Gríðr's. As with the belts of strength, iron gloves appear to be a category of equipment in the mythology's background economy — a giantess keeps a set in her house the way a farm keeps spare tools. The gloves that matter are whichever pair is on Thor's hands when the iron comes flying.
In the primary sources
Járngreipr lives entirely in the Prose Edda. Gylfaginning (chapter 21) names the gloves among Thor's three treasures and states the bare necessity: he cannot grip Mjölnir's shaft without them. Skáldskaparmál contributes the two supporting beams: the tale of the wager that left the hammer's handle short, and the Geirröðr adventure, with Gríðr's loan and the catch of the molten iron. Snorri backs the Geirröðr story with long quotations from Þórsdrápa, Eilífr Goðrúnarson's skaldic tour de force of the late 900s, which narrates the river-crossing and the hall-fight in some of the most difficult verse in Old Norse — proof the adventure is genuinely ancient. The Poetic Edda never mentions the gloves; neither do the sagas. Like the belt, Járngreipr is an artifact we owe to Snorri's care in cataloguing what the god of thunder actually carried.
Legacy
The gauntlet has outlived the god. Marvel's Thor inherited the iron gloves along with belt and hammer, and modern games and retellings keep them in the kit; the broader trope of the power-gauntlet — armored gloves that let a hero grip what no bare hand could — runs through comics and fantasy games with Járngreipr near the head of its family tree. There is also a plainer legacy: every smith who ever picked up hot iron and every welder in modern gauntlets is living the gloves' logic — between great force and the human grip, you put iron. In a mythology where Thor is the god of the working strong, it is fitting that his most modest treasure is protective gear.
Frequently asked questions
What is Járngreipr?
Thor's iron gloves ("iron grippers"), one of his three great possessions with the hammer Mjölnir and the belt Megingjörð. Snorri's Prose Edda says Thor cannot do without them when he grips the hammer's shaft.
Why does Thor need gloves to hold Mjölnir?
The hammer was forged with one flaw — a shortened handle, caused when Loki, as a fly, bit the dwarf working the bellows — and tradition has long read the gloves as the compensation for it. The idea that the hammer returns red-hot is a modern addition, not found in the sources.
What did the iron gloves do in Geirröðr's hall?
The giant hurled a glowing ingot of iron at Thor. Wearing iron gloves lent by the giantess Gríðr, Thor caught the molten iron in mid-air and threw it back — through an iron pillar, through Geirröðr, and through the wall behind him.
Who made Járngreipr?
No source says. Unlike Mjölnir, the gloves have no forging-story and no named smith. The giantess Gríðr owns a pair of her own, suggesting iron gloves were a recognized type of equipment in the myths rather than a unique treasure.
Do the gloves appear at Ragnarök?
No source mentions them there. At Ragnarök Thor kills Jörmungandr with Mjölnir before the serpent's venom kills him; whether the gloves are on his hands for the last blow, the tradition never records.