Stormbreaker is an enchanted axe used by Thor. It was forged from Uru in the heart of a dying star on Nidavellir. Eitri claimed the weapon was meant to become the strongest weapon in Asgard's history.
With Thor and Rocket Raccoon's help, Eitri reignited the dying star and re-lit the forge, melting down ingots of Uru and pouring it into a mold. He then shattered the mold, revealing the axe's blade and weight, but misplaced the handle for the weapon. Seeing that Thor was close to death after taking the brunt of the dying star's power, Groot decided they could not wait for Eitri to find or create a metal handle; he grasped the red hot pieces of metal with one of his arms and then cut the arm off to serve as the handle, truly finishing Stormbreaker. The weapon then revived the smoking husk of Thor, who used its power of the Bifrost to go forth to Wakanda and assist the Avengers.
Stormbreaker was used in the Battle of Wakanda to great effect, augmenting Thor's own lightning massively. Notably, of all the battles, it's the only weapon that severely wounded Thanos by impaling him soon after the Infinity Gauntlet was completed. However, Thor intentionally aimed for Thanos' chest, resulting in Thanos only being badly injured rather than instantly killed. This allowed Thanos to activate the Infinity Gauntlet, and eliminate fifty percent of the universe's life. Moreover, Thanos' otherwise mortal wound was fully healed by the Gauntlet. As Thanos teleported away, Stormbreaker fell to the ground, the blade covered in the Mad Titan's blood.
Stormbreaker is able to focus and enhance Thor's powers. Due to it being composed of Uru, the weapon is nigh-indestructible and able to withstand energy blasts created by the Infinity Stones. It is also able to channel dimensional energy and summon the Bifrost Bridge, which enabled Thor to teleport himself, Rocket Raccoon and Groot to Wakanda.
Like Mjølnir before it, Stormbreaker will return to Thor's hand when summoned, and strikes his opponents with massive force. It glows with an otherworldly blue flame that crackles with electricity, and seems to have the ability to home in on a target if Thor wills it. In addition, the weapon allows the user to fly seamlessly while using it, unlike Mjølnir, which required the user to spin it at great speed to lift them off the ground.
Due to its increased size and mass, having both the blade of an axe and the head of a hammer in its construction, as well as sporting an elongated handle enabling the weapon to be wielded two-handed, it is a notably more potent melee weapon than Mjølnir that came before it. Eitri even went as far as to say Stormbreaker is the strongest weaponry in Asgard's history. As a weapon designed to kill Thanos, it is one of the few able to harm and injure him, with Thor managing to inflict considerable pain and injury when he pushed the axe deeper into the Titan's chest; this would have killed the Mad Titan had he not activated the Infinity Gauntlet. Thanos himself mocked Thor for not aiming for the head, implying that such a blow would have been immediately fatal. Being built to stand against the Infinity Gauntlet-wielding Mad Titan, Eitri enchanted it with several properties that allowed it to take advantage of the weaknesses Eitri had installed into it in order to overpower the Infinity Gauntlet, quickly slicing through the beam unleashed by Thanos, although Thanos was caught off-guard and could have repelled the attack by other ways.
- In the comics, the Stormbreaker was created by Odin as a weapon for Beta Ray Bill, after he returned Mjølnir to Thor.
Behind the Scenes
- When asked how can Stormbreaker overpower the power of the completed Infinity Gauntlet, writers Christopher Markus and Stephen McFeely suggest that Eitri is responsible because of his "Dwarven magic": He made both items and made it so that Stormbreaker was able to defeat the Infinity Gauntlet.
- In a Q&A with Collider, Joe and Anthony Russo answered a question regarding how Stormbreaker was able to take the brunt of six Infinity Stones, replying that it was the greatest weapon ever made and Thanos didn't know what that weapon was and didn't think he knew what he was up against in that moment.
- When asked if Stormbreaker was more powerful than the Infinity Gauntlet, Joe and Anthony Russo responded that it certainly has the ability to counteract the powers of the Gauntlet but the key moment was that Thanos was caught off-guard; he only realized what that weapon was after he got struck by it as it came out of no where.