Howard University Professor of Literature Marc Singer stated Byrne used the character Eternity as a means to "justify planetary-scale genocide".

Before Eternity, there was a single universe, whose animating force was the primal cosmic being that would later call itself the First Firmament.

[19] The first recorded human contact with Eternity is by Doctor Strange, who seeks the entity out when his master the Ancient One is attacked by former pupil Baron Mordo.

After an extended series of battles and a temporary defeat, Strange successfully recruits the X-Men foe the Juggernaut to stop Nightmare from merging his realm with Earth, and together they free Eternity.

[21] The entity is aided by superhero team the Defenders, who locate three missing fragments of its being and convince them to rejoin with Eternity.

[28] Once Thanos is eventually dispatched (courtesy of his own carelessness), Eternity unsuccessfully advises fellow cosmic entity the Living Tribunal against allowing the Infinity Gems to be used in conjunction.

Eternity is imprisoned by the Magus (the evil alter ego of Adam Warlock) who attempts to reunite the Infinity Gems for his own use.

The villain is eventually defeated when Eternity merges with Infinity and together they strip the Magus of his newfound power.

[34] Eternity is eventually killed due to the machinations of his son Entropy, when the later allied himself with Genis-Vell, who at the time was becoming insane under the strain of his cosmic awareness.

Entropy soon regretted what he had done, when all of creation was destroyed, leaving only himself, his sister Epiphany, Genis and Rick Jones, since the prospect of spending the rest of eternity in an empty void was not all that alluring.

After the Crisis was averted due to the Avengers and Justice League joining forces and defeating Krona, the two sadly parted ways.

The pair are opposed by a reuniting of three of the original Defenders (Strange; the Hulk and Namor), with Umar betraying Dormammu and then being defeated in turn.

[42] During the Time Runs Out storyline, the Beyonders are revealed to have killed Eternity as part of destroying abstract entities in each reality across the multiverse.

[44] At the end of the Civil War II story line, Eternity appears before Ulysses when he evolves into a new being and becomes one with the universe.

[45] The cosmic team The Ultimates traveled Outside of the Multiverse to survey the timestream to evaluate its status after the rebirth of reality during the Secret Wars event.

They were rescued by Galactus The Lifebringer, whom the Ultimates had earlier cured of his hunger and transformed into a positive cosmic force, much to the former Devourer's gratitude.

Eternity had used the rescue of the Ultimates as an excuse to lure Galactus there to warn him of his predicament and that all of Creation was in danger from his jailer.

The destruction of the Seventh and the rebirth of the Eighth Multiverse by the Beyonders during the Secret Wars had an unforeseen consequence: It provided an opening for the Firmament, who had been patiently waiting Outside, to attack the newly reborn and therefore greatly weakened Eternity with the goal of destroying the multiverse and restoring itself to the center of creation.

For example, under the Firmament's influence, Master Order and Lord Chaos destroyed the reborn Living Tribunal in front of Galactus the Lifebringer and then found their servant, The In-Betweener and forcibly merged into a new cosmic being many orders of magnitude of power greater that called itself Logos.

Enraged, Galactus devoured Rostov, the Firmament's servant who had infiltrated the Troubleshooters and attempted to manipulate them into defeating the Ultimates.

[47] A black magical item created from Eternity's own substance during the sixth century by a group of renegade occultists to give whoever wears it equal power to anyone they may face, unless they are below the natural ability of the mask's user.

This allowed for example, an untrained peasant to be on equal grounds with the Black Knight and fight him for three days straight.

The entity can manipulate the multiverse to achieve essentially any desired effect, and as its name suggests, it is immortal and unaffected by the passage of time.

The saga is frequently cited on lists of the top Doctor Strange storylines to read,[59] being called "Lee and Ditko’s magnum opus of oddity.

[64] Eternity appears in films set in the Marvel Cinematic Universe (MCU) in varying forms.