Stormbreaker

"A king's weapon. Meant to be the greatest in Asgard. In theory, it could even summon the Bifrost." "Does it have a name?" "Stormbreaker."

- Eitri and Thor

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.

History
"With the iris closed, I can't heat the metal." "How long will it take to heat it?" "A few minutes, maybe more. Why?" "I'm gonna hold it open." "That's suicide." "So is facing Thanos without that axe."

- Eitri and Thor

During the conflict with Thanos, Thor ventured to Nidavellir with Rocket Raccoon and Groot to forge a weapon capable of killing the Mad Titan. Upon arriving, the typically lively forges of Nidavellir were cold and barren, littered with broken parts. The initially scared Dwarf King Eitri found himself reunited with his old friend, and explained that the Dwarves had been rendered all but extinct and his hands had been covered in metal as a result of Thanos's demand for the creation of the Infinity Gauntlet. 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 his fellow Avengers. Stormbreaker was used in the Battle of Wakanda to great effect, augmenting Thor's own lightning massively. It was, notably, the only weapon that caused any noticeable harm to Thanos during the entire conflict: Thor impaled Thanos using it just after Thanos completed the Infinity Gauntlet; however, he intentionally aimed for the chest instead so he could gloat to Thanos, resulting in Thanos only being badly injured rather than instant killed. This proved to be a fatal mistake as the blow could not stop Thanos from activating the Infinity Gauntlet, thus wiping out half the life in the universe before escaping, with the wound closing soon after upon Thanos activating the Gauntlet.

Capabilities
"Wait, what kind of weapon are we talking about here?" "The Thanos killing kind." "Don't you think that we should all have a weapon like that?" "No. You simply lack the strength to wield them. Your bodies will crumble as your minds collapse to the madness."

- Star-Lord and Thor

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. Thanos himself, mocking Thor for failing to prioritize a killing blow, suggested that a strike to the head would have killed him outright. Being build 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 upon Thanos, although Thanos was caught off-guard and could have repelled the attack by other ways.

Trivia

 * In the comics, the Stormbreaker was created by Odin as a weapon for Beta Ray Bill, after he returned Mjølnir to Thor.
 * The MCU version of Stormbreaker shares similarities with the Mjølnir of the Ultimate Universe such as the tip of the hammer.

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 is able to defeat the Infinity Gauntlet.
 * In a Q&A with Collider, Joe and Anthony Russo answered a question regarding Stormbreaker.
 * Audience member: How is Stormbreaker able to take the brunt of five stones?
 * Joe: Of five stones?
 * Audience member: Six stones.
 * Joe: Because it's the—
 * Anthony: Thanos—yeah.
 * Joe: —it's the greatest weapon ever made.
 * Anthony: And also, you know, Thanos didn't know what that weapon was. I don't think he knew what he was up against in that moment.
 * Joe: And Eitri made both [Stormbreaker and the Infinity Guantlet]. Yeah remember that, yep.


 * Shortly afterwards, the interviewer Steven Weintraub repeated the same question explaining he was going to ask it before the audience did.


 * Weintraub: [...] Is Stormbreaker more powerful than the Infinity Gauntlet?
 * Joe: Uh, is Stormbreaker more powerful? Uh, I think...if you watch the film you can see it certainly has the ability to counteract the powers of the Gauntlet.
 * Anthony: I think that key moment though is Thanos is caught off-guard; he literally didn't know the power of what was coming at him. I mean, maybe he could've used the stones to, you know—
 * Joe: In a different way.
 * Anthony: —in another way, had he...understood what that weapon was but it came out of no where.