In the beginning, there was only one universe, the First Firmament, perfect but alone. It decided to create life: Celestial servants. Some of them immediately turned into its servants, and industriously worshiped the First Firmament, seeking its approval whenever they created life on their own, which prompted the First Firmament to name them "Aspirants".
Others, "multicolored rebels", who were "as many as the stars themselves", wanted their own creations to evolve, for the universe to grow, change and die. That was seen by the First Firmament as madness and sacrilege.
At the final battle of the Celestial War, both "Celestials" and Aspirants were desperate. The Aspirants had built the Godkiller Armor, a weapon of such power that made them be able to turn the battle in their favor. However, the suit was stripped to provide key elements for the Aspirants' fleets, and they immediately entered a civil war, which gave the Celestials time to recover and crush their opponents.
The war ended by the defeat of the Aspirants, and the Celestials shattering the First Firmament into pieces: As the rebels detonated their weapons, hundreds of new universes split off from it. The First Firmament fled along with the remaining Aspirants, and the new universes formed a collective entity, the Second Cosmos and First Multiverse.
The Second Cosmos (or Second Infinity) was colonized by the "rebels". Those Celestials evolved their own servitors who they came to call "Omegas", in opposition to the First Firmament, who was the Alpha.
The First Firmament would lurk at the Multiverse during many rebirths, waiting for the right time to strike back, which came after the resurrection from the seventh to eighth multiverse.
- It remains unclear if the Celestial War presented in Iron Man (Vol. 5) #13 is the same conflict that the one of Ultimates 2 (Vol. 2) #6, as the Godkiller Armor was accessed in the Seventh Cosmos.
- The Celestial War seems to be paralleled with the War in Heaven, with the First Firmament representing God, the Aspirants representing the loyal Angels, and the Celestials representing the Fallen Angels.