Stormbreaker

Stormbreaker is an enchanted maul used by Thor. It was forged from Uru in the heart of a dying star on Nidavellir.

History
During the conflict with Thanos, Thor ventured to Nidavellir with Rocket Raccoon and Groot to forge Thor’s new weapon. 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 fused off with metal as a result of Thanos’s request of the forgery of the Infinity Gauntlet.

With Thor and Rocket Raccoon’s help, Eitri reignited the dying star and re-lit the forge, creating Stormbreaker with a handle made from Groot’s Arm. The then smoking husk of Thor was revived and used the power of the Bifrost to go forth to Wakanda and assist his fellow Avengers.

Capabilities
Stormbreaker is able to focus and hone Thor's powers, acting as a conduit. The weapon, due to being made out of Uru, is neigh-indestructible and able to withstand energy blasts created by the Power Stone, even wounding Thanos.

Stormbreaker is able to channel dimensional energy and act as a Bifrost Bridge, shown when Thor teleported himself, Rocket Raccoon and Groot to Wakanda instantly.

The weapon, like Mjølnir before it, will return to Thor’s hand when he opens it and strikes his opponents with massive force.

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.