The big question most people would ask when they see a new weapon like this is who will wield the thing?
Reddit user BenjaminButtcrack (ugh) has produced a fantastic fan theory and it’s truly compelling.
In Infinity War, we see Thor gain a shiny new weapon called Stormbreaker, forged in the power of a star by the dwarven smith Eitri played by Peter Dinklage.
Benjamin eludes to a particular scene in the forging process of Stormbreaker, and points out what could be either an innocent editing mistake, or what’s more likely when dealing with Marvel production teams, an Easter egg. In the forging scene when Eitri is pouring the molten metal into it’s mold, he fills not one but two molds, but only proceeds to smash open one of the two to produce Stormbreaker, this can be seen below.
Source: Infinity War/Reddit
We know the first mold held Stormbreaker, which belongs to Thor, the presence of a second mold would suggest another weapon being made by Eitri, and with his resume of making Mjolnir, the Infinity Gauntlet and Stormbreaker, if this is the case it should be a very powerful entity.
Stormbreaker was forged to be a super weapon that is able to defeat the power of Thanos’ Infinity Gauntlet, with all 6 infinity stones. If Eitri made Stormbreaker a twin weapon when it was forged then it’s only reasonable to assume it would be incredibly powerful, at least powerful enough to sit among his other creations like Mjolnir and Stormbreaker.
In Infinity War, Thor reveals to the Guardians of the Galaxy that star-forged weapons like Stormbreaker (and whatever it’s potential twin is called) cannot be wielded by normal mortals, and as a result we’re able to narrow who this weapon could belong to, but the most likely answer seems to be the newest edition to the MCU, and the only other member of The Avengers capable of wielding Asgardian weaponry, Captain Marvel.