Járngreipr, meaning iron gripper in Old Norse, are the iron gloves used by the god of thunder, Thor. According to the Prose Edda, along with the hammer Mjölnir and the belt Megingjörð, Járngreipr is one of Thor's three crucial possessions.
These gauntlets are said to be the only known items which are capable of allowing the wearer to wield Mjölnir without any ill-effects. The gloves themselves possess magical properties, as they are able to let the wearer wield not just Mjölnir, but any divine weapon forged by the gods without having to face severe consequences afterwards.
In Norse mythology, Thor uses the gloves to wield Mjölnir, therefore the origin of the gloves and the reason for this may come from the forging of the hammer, when Brokk, the dwarf working the bellows was bitten in his eye by a gadfly, being Loki in disguise, which caused the handle of the hammer to be shortened. But despite this, the hammer did not lose its properties and was still a mighty weapon to be feared, so much so that it required these special gloves to wield it and use its power, even by one as powerful as Thor himself.
The gauntlets allow the wearer to wield Mjolnir, Thor's hammer. Without them it would be rendered useless as its impossible to use otherwise. The gauntlets also bestow enhanced strength, though in reality the gauntlets react with a certain type of rock making the mass of the rock incredibly less, thus enabling the wearer to move what appears to be colossal amounts of weight. When the gauntlets react with the rock, they and the rock give of a blue glow and a smooth humming noise.