WARNING: The following contains spoilers for Thor #14, by Donny Cates, Nic Klein, Matt Wilson and VC's Joe Sabino, on sale now.
In Thor #13, of Asgard, Donald Blake, Thor's corrupted human alter ego, threatened to destroy the World Tree itself . Thankfully, a coalition of heroes comprised Doctor Strange, Valkyrie, Lockjaw, Loki, Throg, Odin and the rest of Asgard's forces appeared on the Rainbow Bridge, ready to stop the all-powerful Donald from securing his victory. Even Thor himself joined the battle, by remote piloting the Destroyer armor from his magical prison. Now, in Thor #14, the fight for Asgard begins, and Donald Blake uses his powers to call Thor's hammer, Mjolnir, to him.
Blake isn't exactly worthy to wield the hammer, but he has harnessed the Odin-Force within himself, which is what allows him to manifest the weapon. But, in the battle, another hero proves himself worthy by wielding Mjolnir once more: Beta Ray Bill.
Beta Ray Bill is a Korbinite alien who proved himself worthy of lifting Mjolnir a long time ago. After forming a bond of trust with Thor, Bill would get his very own hammer, Stormbreaker, to carry as a hero of the cosmos. However, the relationship between Thor and Beta Ray Bill was recently tested in the pages of Donny Cates and Nic Klein's Thor. Indeed, when the series began, Thor agreed to become the new Herald of Galactus in order to stop the Black Winter. While Thor reluctantly became an agent of the Devourer of Worlds, Beta Ray Bill attempted to stop him. In their fight, Thor used his new cosmic abilities to destroy Stormbreaker, leaving Bill without a signature weapon.
Thor would later make amends for this act by naming Beta Ray Bill Asgard's new Master of War, shortly before Donald Blake would unleash his rampage across the Realm Eternal. Now, in Thor #14, Beta Ray Bill is among the warriors who join forces against Blake, and while he may not have Stormbreaker at his side, he demonstrates once more his worthiness by calling Mjolnir to him.
As the battle begins, Donald Blake manifests Mjolnir to battle the Destroyer armor. Eventually, Blake drops the hammer, and he grabs hold of the armor, getting ready to absorb the Odin-Force that powers it. However, the former All-Father himself, Odin, intends to put an end to the fight by summoning Mjolnir to him. However, the hammer doesn't fly to his hand. Instead, it's Beta Ray Bill who catches it, saying he is still owed a weapon for the one he lost.
With a thunderous blast, Bill transforms from his humanoid look to his horse-faced form, and his red mane-adorned helmet makes a triumphant return. With a throw of the weapon, Bill puts an end to the fight, knocking Donald Blake down, which gives Doctor Strange the time to restrain the villain. Shortly after this, Thor finally returns from his magical prison, and he calls Mjolnir to him, claiming the weapon to deliver his final judgment on Blake.
Therefore, Beta Ray Bill's claiming of Mjolnir is incredibly short. But the moment still packs an important punch. It shows that after everything the character has been through recently, he is still very much worthy of the hammer. After all, Beta Ray Bill had the strength and the courage to stand up to Thor himself when the God of Thunder became the new Herald of Galactus. Even though he ultimately lost that battle, Bill was still in the right, and he continued to prove his heart was steadfast.
This brief moment where Bill wields Mjolnir is a confirmation of everything we know about him. Without Stormbreaker, he could easily be the one to wield Mjolnir going forward, but part of what makes him worthy of Thor's power is his understanding that the hammer will always truly belong to Thor.