Eternity was the embodiment of the Seventh Cosmos and sixth Multiverse alongside Infinity, with whom he was one.^[5] As the Seventh Cosmos, Eternity was all that existed along the fabric of time^[14] across the entirety of the Multiverse,^[15] having been formed to ensure the boundlessness of creation.^[2] As a result, Eternity came to embody the Multiverse across all its planes and levels.^[16]

Torn by the cosmic solitude begotten by his nature as the embodiment of all existence, and wishing to experience the mortal feelings of struggle, love and otherness, Eternity created shells for himself, each one infused with an infinitesimal portion of his endless consciousness, and scattered them across the entire Multiverse. Having imposed duality over himself and experienced the sensation of struggle for the first time, Eternity pulled his shells back into himself, realized how blissful his unfettered and unlimited existence truly was, and was finally at peace with himself. However, Eternity soon realized that three of his avatar forms had not returned to his psyche, and sensed necromantic forces at work keeping them from doing so. Due to the nature of the Multiverse, were he not to recover those three avatar forms and merge them into his infinity once more, reality would deem itself incomplete and the Multiverse would be destroyed. Therefore, Eternity called out to the human sorcerer Stephen Strange in his dreams and asked him to seek out his avatars in order to prevent all of creation being consumed into the void. As events turned out, however, there were no external forces holding back the children of Eternity; they were simply too enamored with the conjoined nature of human existence to return to the infinite solitude that Eternity represented. Eventually, the human hero Kyle Richmond convinced them to return to their original form, saving the multiverse and letting Eternity find oneness within himself once more.^[17]

The cosmic entity Abraxas, an embodiment of destruction, who had been freed from his imprisonment due to the recent death of Galactus, sought to use the Ultimate Nullifier to destroy the multiversal incarnation of Eternity, but was stopped after Franklin Richards and Valeria resurrected Galactus, and Reed Richards used the Nullifier to recreate the multiverse/Eternity without Abraxas as a part of it.^[18][19]

Eternity had his solitude as all that existed interrupted once again when Dormammu, who came to be empowered by a disturbance in the cosmic order of reality, and his sister, Umar, used the dimensional magic of the Eye of Agamotto to create a gateway into the realm outside all space and time where he was. Offended, Eternity demanded them to return to himself as they were mere thoughts within his consciousness. They rejected his offer and used their newfound powers to defeat him. Blinded by his lust for power and control, Dormammu immersed himself in the essence of Eternity's core and absorbed all of his powers in order to recreate the entire Multiverse into his own image.^[20] Upon defeat, Dormammu claimed to have returned the infinite energy he had stolen from Eternity, presumably restoring order to the Seventh Cosmos in the process.^[21]

During the Chaos War, Amatsu-Mikaboshi, an aspect of Oblivion,^[22] successfully destroys almost the entire multiverse, but it is restored through the efforts of Hercules using up all of his power as the then most powerful skyfather.^[23]

Following the destruction of the Multiverse at the hands of the Beyonders,^[24] and its restoration by The Molecule Man,^[25] Eternity became the embodiment of the Eighth Cosmos and seventh Multiverse^[26] while Infinity moved on to the Far Shore.^[5] Left weak after his death and resurrection, Eternity was chained up by the First Firmament, the first universe to ever exist. It had been watching from the void as the Multiverse passed through each renewal cycle in the hopes that one day it would reclaim his place as everything that is. To accomplish its mission, the First Firmament sent its Aspirants to destroy Eternity from the inside out.^[26]

When the Ultimates set out to exit the Multiverse in order to assess the damage time-travel had caused to it, Eternity asked Galactus to stop them.^[27] After returning the Ultimates to Earth, thinking Eternity simply didn't want their minds to bear the full scope of witnessing reality from outside, Galactus was made the sole confidant of Eternity's new and unusual restriction, and was tasked with finding the being responsible for it.^[28]

Galactus gathered Ego-Prime, Psi-Hawk, the Infinaut, and the ghost of the Shaper of Worlds to form the Eternity Watch in order to help Eternity.^[29] The Eternity Watch subsequently confronted Logos and the First Firmament's Aspirants in the Superflow. At the same time, the Maker foolishly used the High Evolutionary's technology to bring down the Superflow in an attempt to unify the Multiverse into a single reality and strengthen Eternity.

When this process proved to be counterproductive and actually began to damage Eternity even further, Galactus had the ghost of the Shaper of Worlds teleport the Ultimates to the High Evolutionary's Counter-Earth.^[30] With the help of another group of Ultimates brought back to life by the Maker, who subsequently rebelled against him, Galactus' Ultimates managed to reverse the damage caused to the Superflow and restored the Multiverse to its normal state.

Galactus and the Eternity Watch subsequently resumed their confrontation against the agents of the First Firmament. With the help of Black Panther's ascended astral form and the rebirthed Celestials, the Eternity Watch defeated the Aspirants and Logos. The First Firmament was also defeated, when Eternity summoned the past incarnations of the Multiverse to his aid, the Ultimate Ultimates.^[5]

By virtue of the fact that all Manifestations of Eternity are merely cells within him,^[6] he has all the powers and abilities of his lesser iterations across the Multiverse, and possibly the power of every entity residing within the Multiverse, since all entities in creation are said to be mere thoughts generated within the expanse of his consciousness.^[31]

Eternity was temporarily weakened when the Multiverse was reborn as the Eighth Cosmos.^[26]

• Although this multiversal Eternity did not appear until Ultimates (Vol. 3) #5, the fact that such a being existed was established in the second story in What If? #43. When Doctor Strange, the Silver Surfer and Phoenix planned to use the Ultimate Nullifier to restore their universe (which had been destroyed by Korvac in What If? #32), the spirit of the universe that had once existed there manifested itself and asked them to not restore it. While making its plea, this spirit identified itself as "an aspect of all Eternity" and referred to "the nigh-infinite number of aspects that comprise(d) its totality."