It’s interesting to think about but not a sure thing if the MCU is going to go to the lengths it might require to bring in the First Firmament, the embodiment of all that is, who is credited with creating the Celestials. Quite a few fans might wonder what could possibly create such powerful beings that have so much control over creation, but the truth is that they were created by the First Firmament, which is essentially the same as the character Eternity, only this being was the first to take on such a role. But the Celestials were created by the First Firmament in order to stave off the loneliness of being one of the most powerful beings in existence and to do its bidding as well. Eventually though, the Celestials did break away from the control of their master and became their own species, as at some point the First Firmament became replaced over time as the multiverse was created. When one thinks about how each facet of the multiverse represents a different universe, it’s easier to think that there are several beings like Eternity that exist side by side, but going too far into can confuse a lot of people since there are a lot of questions to consider.
But as grand and enigmatic as they are, the Celestials started out as servants, and in a way, they still are since they’re bound within the essence that is Eternity, the embodiment of the universe that is the MCU. The Celestials are powerful beings that are able to do things that are far beyond the capabilities of even their most powerful creations, but since they’re creations as well they do have limits, even if they’re hard to see. Trying to force the human mind to conceive of anything creating what are essentially gods is a bit tough for many since it requires a level of thinking that makes it clear that as low on the hierarchy as most Marvel heroes are, the Celestials are still on that ladder as well, no matter that they helped to facilitate the existence of much of the Marvel universe as the story goes.
Much of the time, beings such as the First Firmament and Eternity don’t really involve themselves with what’s going on within their own realities, which to say, the embodiment that they represent. They’re content to let things go on as they will unless there’s a true threat to their existence, which is rare since the power that each of them holds is so immense that it defies easy explanation. But the fact is that there are threats out there that are capable of damaging or even harming such beings, and it was brought up in the Infinity Gauntlet series since when Thanos gathered the Infinity Stones and placed them in the gauntlet, he took on pretty much everyone that came at him, including the Celestials and including Eternity and many other cosmic beings that thought their power was far greater than what it was. Thanos actually took Eternity’s place and swatted the Celestials like they were nothing in the comics, but it’s fair to think that such a thing wouldn’t have happened this time around since the MCU has been gaining ar reputation by dampening the powers of some characters and amping up others as they see fit.
But the point to all this is that the Celestials were created, they didn’t just appear suddenly without any reason. In the time since their creation, they went on to become mysterious beings that many knew next to nothing about while others had an idea of what they could do but might have never seen such a thing. So far in the MCU, they’ve been seen as all-powerful beings that can do pretty much anything they need to, but the question of their origin was one that was bound to come up, since just about everything has a beginning point, and we have learned at this time that they are birthed from the core of a planet and end up destroying said planet in order to create other solar systems as they continue the cycle. In a sense, the Celestials do not fight the nature that was bred into them since they continue to do the same thing they were made for over and over.
It’s kind of ironic that their own creations, the Eternals, would rebel against them when they in turn rebelled against their creator. It’s also very telling since it appears to be a natural reaction that is found in every living creature to some degree since the act of pulling away from one’s creator has been seen as a rite of passage as well as a bid for independence. There was obviously a time when the Celestials were no better than children of another being, and like all kids, they eventually wanted their freedom.