During the 11th Century, Thor faced off with the Celestial-powered being called Apocalypse. Seeking revenge, Thor blessed Jarnbjorn with his own blood, giving it the power to pierce Celestial armor. Eventually Thor lost Jarnbjorn. Kang the Conqueror recovered Jarnbjorn from Baron Mordo's tomb in Brazil.
The axe was then stolen from Kang by the Apocalypse Twins during their training under him. Uriel and Eimin used the weapon to kill the Celestial Gardener outside the Starcore space station, and became the new Apocalypse. This murder was part of an elaborate plot concocted by the twins to frame Earth for the death of the Celestial Gardener so the Celestial Exitar would destroy it. The Twins then convinced Scarlet Witch to cast a spell that transported every Mutant on Earth to their ark so mutant-kind would survive while humanity was destroyed with the Earth.
In a divergent universe, their plan would've succeeded, but from the said universe, the remaining members of the Avengers Unity Division arrived and thwarted the Twins' plans. Thor reclaimed Jarnbjorn and used it to kill Exitar by striking him in the neck.
Jarnbjorn was replaced in the Asgardian armory. When Thor could no longer wield Mjolnir after his battle with Nick Fury on the Moon, Thor took up Jarnbjorn once again. While fighting Malekith and a force of Frost Giants under the sea, Malekith took Jarnbjorn from Thor and used it to cut off his left arm.
Forged by Dwarves, Jarnbjorn is naturally sharper than almost any Earthly weapon, and can cut virtually anything. In addition, Jarnbjorn has a charm placed on it that makes it indestructible, and it can be used to defend against any attack, even bursts of energy like Apocalypse's optic beam. Thanks to Thor's own enchantment, Jarnbjorn can pierce the armor of Celestials or created using Celestial technology.
- "Jarnbjorn" means "Iron Bear" in Old Norse, as well as some modern nordic languages, although in modern Norwegian/Swedish it would be spelled Jernbjørn/Järnbjörn.
- The weapon's name might be a reference to Jarnsaxa, Thor's giantess lover from norse myth.
- 99 Appearances of Jarnbjorn
- 6 Minor Appearances of Jarnbjorn
- 4 Media Jarnbjorn was Mentioned in
- 96 Images featuring Jarnbjorn
- Item Gallery: Jarnbjorn