First Firmament

The First Firmament is a sapient universe, the oldest known entity in the Marvel franchise, which conspired to consume and digest the Multiverse.

Origins and history
Given that everything in the Marvel continuity was ultimately created by the unknowable One above All, presumably he created the universe which would eventually come to be known as the First Firmament. Self-aware from the start, it created within itself living beings, star-spanning space gods which worshipped the universe which had spawned them, and created smaller lifeforms in imitation of it, and which it called 'Aspirants'.

However, inside the First Firmament there also lived other beings, god-like giants like the Aspirants, but decidely different: they did not worship the universe, let alone obey it, but rather desired freedom and independence. These colorful beings would eventually come to be known as the Celestials. The Aspirants and the Celestials waged war over their ideas; one side fought for order and obedience, the other for freedom. The conflict ended up being so devastating, it rended the universe apart; the substance of the First Firmament spilled into the void like blood, where it eventually coalesced into a host of new universes!

Soon, the newly-formed universes drew together into a Multiverse, self-aware and possessed of life as their predecessor had been, manifesting the being known as Eternity - the first iteration thereof. The Celestials migrated to this new Multiverse and from then on dedicated their efforts to maintaining its structure, while the First Firmament withdrew iinto the darkness to lick its wounds.

In the infinitude of eons that followed, the First Firmament and its servants the Aspirants observed the Multiverse with hungry eyes. Hope rose as the Multiverse collapsed and died, but fell again as it manifested anew in a different form; this happened over and over again, and each time the Multiverse and Eternity were reborn more complex, more perfect and seemingly more unassailable. But the First Firmament - presumably it took this name when it realized it had successors now - sent out its Aspirants to attack the Multiverse, weaken its structure, and slay its defenders. So, the Aspirants came to be known to the beings who lived inside the Multiverse as 'Death Celestials' since they appeared as dark, forbidding versions of the (already perceived as evil by some) Celestials.

After the death of the seventh iteration of the Multiverse (the original Multiverse, however, is held to be the second one), the First Firmament finally saw its chance. Due to unusual circumstances - at the hands of whom else than Doctor Doom, - the Multiverse was slow in reforming, and the Celestials were unattentive due to not yet existing at this time, allowing its progenitor to proceed an attack. When the Multiverse did reform, Eternity found itself in chains, unable to act as some of its components were corrupted by the Aspirants. Chaos and Order assassinated the Living Tribunal, the cosmic arbiter, and claimed the title of supreme authority for themselves as the entity the Logos. In this role, they proceeded to eradicate the Celestials (although unknown to the Logos, one of them survived due to intervention by the Never Queen). Through shrewd manipulation of many agents, the First Firmament then managed to cause the collapse of the Superflow, the medium which keeps all universes in the Multiverse separate.

The effect of this was to transform the Multiverse into a universe; all of its volume and mass, all of its life and power, now all in a single universe instead of myriad. While the instigator of this, the villainous Maker, had believed this would create a more powerful, unified Eternity - his 'Ultimate Universe' - it in fact allowed the First Firmament to begin to consume and digest the new universe. With its defenders either corrupted, destroyed or incapacitated, Eternity seemed doomed.

However, the Ultimates - a team of cosmic heroes, created to take on the ultimate threats - managed to provoke Eternity back into action by using the very machinery the Maker used to stir its mind. Eternity, aware again, broke free from the First Firmament's deadly embrace and began to reconstitute itself as a Multiverse. Frustrated, the First Firmament decided that since its plan to simply reabsorb what it had lost so long ago had failed, it would now simply destroy it; but Eternity, who had been warned by the Ultimates' ghostly messenger the Shaper of Worlds, called out to its final helpers: the manifestations of the multiverses that had come before him. Proclaiming that nothing ever truly dies, they overwhelmed and restrained the First Firmament, before taking it away to an incomprehensible, unknown reality which, apparently, is the Afterlife of entire multiverses.

Appearance and abilities
From within, the First Firmament appeared as a universe, although far more vast than the universe most beings know, since its substance was more vast than that of Eternity even though the latter embodied a Multiverse. Manifesting in a form capable of interacting with others, the First Firmament appeared as a monstrous version of Eternity with a grotesque, animal skull-like face with a large toothed maw and three eyes, and clawed hands.

Being an entire 'super-universe', the First Firmament possessed incomprehensible power of the highest order, including - by definition - any power and ability that is thought of as such. Even among the small group of beings like it, it stood as powerful, although perhaps not as the most powerful, since it hesitated to attack Eternity in its prime. It could create life that, itself, would be viewed as gods by mortal beings.