Contains spoilers for Defenders: Beyond #2!
After decades of mysteries and never fully confirmed theories, Marvel Comics finally explains the origins of the Multiverse and the Celestials all at once. While Marvel cosmology is fascinating, it can get a little complicated, especially for new fans. Now, thanks to writer Al Ewing and artist Javier Rodrìguez, there is one coherent tale of how it all began, and it connects the Celestials and the Multiverse in fascinating ways.
The Celestials were created by the legendary Jack Kirby in the pages of The Eternals #2 (1976). True to their creator's unique brand of sci-fi mixed with religious themes, the Celestials are space gods who experiment on the primitive creatures of Earth, creating two different races: the perfect, immortal Eternals and the hideous Deviants. The mystery behind the Celestials' true origins was part of their mystique, but that did not stop Marvel from retconning their story many times. The last explanation came from Al Ewing, in the pages of Ultimates 2 vol. 2, where the Celestials were presented as a rogue faction of the Aspirants - the first beings created by the First Firmament, the personification of the first iteration of Marvel's universe, the First Cosmos.
Defenders: Beyond #2, written once again by Al Ewing and drawn by Javier Rodrìguez, confirms everything that was explained in Ultimates and adds more interesting details. While the Aspirants worshiped their creator, the Celestials wanted to pursue their own desires and have the life forms they created evolve and die. This enraged the First Firmament, which did not possess the concept of change, and sparked the Celestial War, leading to the destruction of the First Cosmos and the creation of the Second. With the shattering of the first universe, where change and evolution did not exist, something different was born: "a multiverse of possibility, where each 'what if' could become its own 'what is.'"
Ewing thus finalizes his ambitious re-conceptualization of Marvel's cosmology that began in Ultimates and further developed in Defenders and Defenders: Beyond. Over the decades, Marvel stories showed several theories and hypotheses behind the Celestials' origins, but Ewing's is the only canon one, as it connects the powerful creatures with the larger mythos of Marvel's cosmology and its cyclical nature, which is central to Ewing's stories. The Multiverse also had conflicting origin stories until now. The first one, presented in the classic Thanos Quest miniseries by Jim Starlin and Ron Lim, saw it as the result of the self-immolation of the first being in creation, Nemesis. Another explained the Multiverse as a creation of the Celestials, but in this case to trap their flawed and dangerous servants, the Exterminators, in a sealed reality.
The origin story presented in Defenders: Beyond, however, should be considered canon, as it is the most recent and also the most coherent with Marvel's overall cosmology. The shattering of the First Cosmos introduced the concept of change that sustains the Multiverse. This explanation also confirms the fundamental role of the Celestials, who are essentially responsible for kickstarting the cycle of life, death, and rebirth that is the basis for Marvel's Multiverse.