An elder god in the shape of a cosmic thunderstorm,^[5] according to the records of Omnipotence City's Halls of All-Knowing, the God Tempest, or the Mother of Thunder, had existed since the dawn of time and grew gradually in size with each eon that passed. The worst of its wrath was reserved for those who truly deserved it, which made people believe it had a mind of its own.

On its path of destruction, the God Tempest eventually reached Asgard. The All-Father Odin confronted the storm and fended it off for days with the power of the Odin-Force. Once the storm grew tired and weak, Odin struck it with a nugget of Uru which had been gifted to him by the Dwarves of Nidavellir. Through means of dark and primal magic, the storm became entrapped inside the Uru.

Odin subsequently took the piece of Uru back to the Dwarves so they could forge it into a weapon through which Odin could wield the storm's power. After seventeen weeks of forging, during which the Dwarves had to use the power of a star to reshape the metal, the piece of Uru was transformed into a hammer, which Odin dubbed Mjolnir. However, the storm still raged inside the mallet, and Odin failed to contain it, forcing him to enchant it to prevent anybody else from lifting it.^[6] For a time, Odin wielded Mjolnir during his tenure as one of the prehistoric Avengers, but the God Tempest often attempted to rebel against him.^[7] Once he ascended to the throne of Asgard, Odin left Mjolnir to sit in the weapons hall of Asgard for ages. According to the Lord Librarian, the God Tempest eventually died, and only its power remained within Mjolnir.^[3]

The hammer would become the weapon of Odin's son Thor, who proved himself worthy to bypass the hammer's enchantment.^[8] Many ages later, the hammer appeared to have regained its sentience. After Thor lost its ability to wield it, the hammer also rejected Odin's grasp.^[9] Mjolnir found a new owner in the form of the mortal Jane Foster, and even temporarily took her appearance and impersonated her to protect her identity as the new Thor, an action the hammer expressed to be unable to replicate without a century of rest or so.^[10]

The God Tempest was liberated when Thor hurled Mjolnir into the Sun to kill the Mangog, an incident that also resulted in her death since her body could only withstand reverting to her human form one last time. Odinson attempted to channel the God Tempest to use its power and bring Jane back to life, and was only successful when Odin joined his endeavor. Following Jane's resuscitation, the God Tempest's power was depleted, and it became nothing but a breeze.^[11]

During the final battle of the War of the Realms, the God Tempest manifested once more in the Sun -- where it was commanded by Thor to reforge Mjolnir.^[12] The God Tempest indwelled the hammer once more,^[13] and in the process merged with the essence of the Mangog, imbuing the hammer with a bloodthirsty consciousness and corrupting Odin's enchantments. Growing bored of Thor's duties as the king of Asgard,^[14] Mjolnir rejected Thor as a worthy wielder while letting anyone other than him wield it.^[2] Seeking to throw Asgard into chaos by destroying Odin's works, Mjolnir secretly let Jormungand into Donald Blake's metaphysical prison, enabling Blake to steal the dragon's power and wreak havoc when he escaped.^[1] When Thor abandoned Mjolnir at Avengers Mountain,^[15] the divine hammer manifested a feminine body from the divine lightning of the God Tempest contained within it, becoming the God of Hammers prophesied to bring ruination to Asgard. The God of Hammers carried out a genocide against the dwarves of Nidavellir before embarking on a campaign of slaughter across the Ten Realms, framing Thor for the attacks in order to instigate a new War of the Realms against Asgard. After laying waste to Broxton, Mjolnir attacked Thor when he tried to call the hammer to himself, revealing that it was the God of Hammers.^[16]

Odin and Sif intervened when Mjolnir tried to kill Thor, using the Bifrost to send the divine hammer to the Void beyond the edge of the universe. However, Mjolnir returned to Earth in seconds and vengefully broke Odin's spine in retaliation. Thor's allies attempted to intervene, but she effortlessly defeated them before Thor called on the aid of Gaea to bury Mjolnir under a mountain of debris and boulders. Just as she broke free, Odin sacrificed himself to transfer the rest of the Power of the All-Father to Thor, leaving Mjolnir horrified.^[17] The enraged Thor used the Bifrost to teleport the God of Hammers to the forge in Nidavellir where Mjolnir was created, and then used the Power of the All-Father to ignite the forge with the heat of a billion suns. Taking Mjolnir from the God of Hammers, Thor used the forge's heat and the Power of the All-Father to burn Odin's enchantments and the God Tempest's corrupted essence out of the hammer, shattering it in the process.^[18]

The God Tempest was a cosmic storm the size of a galaxy. According to the Halls of All-Knowing, "its winds blew comets off course, ripped worlds from their orbit, and snuffed out stars like flickering candles." Its lightning was capable of turning moons into dust, and its thunder made black holes tremble. It took Odin all of his forces and days to contain it.^[10]