An absolute truth in the Marvel Universe is that there is always a greater power. While it may seem impossible that there could be forces greater than beings such as Thanos, Galactus, and the countless cosmic entities that exist amongst the stars, the Marvel universe possesses a history that reaches back beyond its very creation. Those that existed before existence are known as the Celestials and they have been some of the most powerful forces in the Marvel Universe since they were created by Jack Kirby in 1972's Eternals #2.
The Celestials as a race were created in what was known as the First Firmament, the manifestation of the very beginning of existence. The First Firmament was responsible for the creation of both the Aspirants and the Celestials, beings both intended to serve it. The Celestials rebelled against the First Firmament and the Aspirants, sparking what would become known as the Celestial War. From this war came the birth of the multiverse and the foundations of known reality.
As the Celestials have survived throughout all of existence they have witnessed the creation and destruction of planes of existence far beyond the realms of mortal comprehension. The ideas of life and death and the conjurations of divine realms of afterlife from the perspective of organic minds is woefully insignificant to the Celestials. The greatest and most splendid representations of life are of little regard to them as they exist on a plane infinitely beyond everything else.
In order to better understand and study the organic life within the universe, the Celestials have at times created life of their own. The powerful races known as the Eternals and the Deviants were the products of their experimentation. The Celestials conduct what is known as the Celestial Hosts, events in which they travel from planet to planet in order to inspect and study the life that has grown there. If deemed worthy, those living on the planet continue on; for those deemed unworthy, they are eradicated down to their very atoms.
In Infinity Gauntlet #5 (by Jim Starlin, Ron Lim, and Josef Rubinstein), the battle against Thanos had risen to such heights that even Galactus and the Celestial Abstracts stood before The Mad Titan. As two of the Celestials, The One Above All and Ziran the Tester, engage Thanos in battle they resorted to throwing entire planets at him as a means of attack. It is noted that the Celestials did not care if the planets were inhabited with intelligent life. As planet after planet is hurled at Thanos they each explode, snuffing out innumerable lives, cultures, and histories.
It is a chilling sentiment to hold and a harrowing knowledge to live with in the Marvel universe. With absolutely no shred of doubt it has been proven how worthless life truly is on the universal stage. Standing above the pantheons of deities that are worshiped on every planet in the heavens, the star gods themselves view life as nothing more than an interesting experiment or diversion. The greatest battle some of the universes’ heroes have ever fought was against their primordial progenitors in a dire effort to defend their right to exist.
In a paradoxical manner, to battle for the worth of one’s very existence is in itself proof of its value. On the grand cosmic scale it is understandable why the Celestials would view simple organic life as inferior. But it is the burning desire of that life to survive that gives the Celestials pause, and it is the ferocity with which that life fights that proves its place in the overall cosmos. For all their power, even the Celestials have tasted defeat at the hands of the life that they have deemed inconsequential. With The Eternals and Guardians of the Galaxy Vol. 3 coming soon, the true power of the Celestials may finally be witnessed in the MCU, bringing with it a time for Marvel's heroes to fight harder than they ever have before.