Warning: SPOILERS for War of The Realms #6
The mighty Thor has gotten a brand new Mjolnir in Marvel's Universe, and this hammer is more powerful than any that has ever come before. Not only is it the weapon that helps Thor end the massive War of the Realms, but proves once and for all what it means to be truly 'worthy.'
It's a creation years in the making, with writer Jason Aaron spending the last seven years redefining Thor's mythology. The Aaron run saw Thor fall further than ever before, coming to realize he was unworthy to wield his enchanted hammer. Mjolnir evidently agreed, and to Thor's heartbreak he found himself unable to pick it up off the surface of the Moon. Mjolnir was eventually lifted by another, even greater Thor in Jane Foster, who (with Thor Odinson's blessing) became the Goddess of Thunder. A duty she held until being forced to destroy Mjolnir to kill the Mangog. But that was the old Mjolnir...
War of the Realms #6 sees Thor regain Mjolnir, using the sun itself as a forge in which to remake the hammer. But there is a larger, far more crucial difference between the Mjolnir of the comics and the MCU; in the comics Mjolnir is a cosmic power in its own rite, after Aaron revealed that the enchanted hammer contains The God Tempest, sometimes called the Mother Storm--a power that can harm even the famous Phoenix Force and match Odin the All-Father himself. Odin had trapped the God Tempest inside Mjolnir years ago, and the hammer's destruction had released it into the sun. But this time? The God Tempest cooperates with Thor in the forging, and indeed chooses to incorporate itself into the new Mjolnir.
Jason Aaron's run has shown just how powerful Mjolnir could truly be; unlike the Odinson, Jane Foster (before her death) was a partner with the hammer, and she allowed Mjolnir a lot of leeway. As a result, it served her with distinction, performing feats that left Thor staggered. On some occasions, it was the hammer that showed Jane where she was needed, guiding her from realm to realm. Presumably, Mjolnir had never done that before either... because, on some level, the God Tempest resented being trapped inside a hunk of Uru. Now it has chosen to return to the hammer, and to partner with Thor Odinson. Jane Foster's feats are now open to Thor too, with the added detail of the handle of the new Mjolnir made from a branch of Yggdrasill, the World Tree, which had been regrowing in the heart of the sun. This is as much an energy field in its own right as a tree, binding the Ten Realms together.
In the aftermath of "War of the Realms," Thor Odinson now wields the most powerful version of Mjolnir ever. He holds in his hand a weapon that contains enough power to match Odin blow-for-blow, a cosmic storm that can blow planets off their axes. Crowned All-Father of Asgard, this Thor is truly Marvel's mightiest hero.
War of The Realms #6 is available now from Marvel Comics.