The Marvel Cinematic Universe is on the cusp of delving deeper into some of the most powerful beings ever, the Celestials. Initially teased in the first Guardians of the Galaxy, these beings possess immense strength and even the potential to destroy and create entire planets. In the comics, they have even had a hand in influencing the creation of the Earth. However, movie fans have only caught a glimpse of this power.
In Guardians of the Galaxy Vol. 2, Star-Lord's father, Ego, is an altered version of the comics character, Ego the Living Planet. In the film, he is a Celestial and can manipulate matter to create his own humanoid form. He also has the ability to spread his cells to other planets and, with the help of another Celestial, expand his mind across the universe to engulf other planets. Additionally, Ego doesn't know of any other living Celestials.
Though Ego is not considered a full God in the MCU, the Celestials' powers in the comics allow them to control the creation and formation of matter. They also possess immense cosmic power and can even create entire pocket universes. Considering they're basically immortality, they are also extremely hard to kill. Since most members of the species were created within the known universe, they are just a step below divine deities like The One Above All.
In the films, the full range of the Celestials' powers has not been revealed. Nevertheless, viewers have gotten an idea of the size and magnitude they carry. In the MCU, Knowhere is a spaceport that is housed inside of the head of a dead Celestial. Its resources are precious and based on the size of the head, the creature itself is massive. Another Celestial was shown destroying a whole planet using the power stone. For now, the exact whereabouts of the beings in the MCU are unknown, but that may not last forever as the films begin to reach out into the depths of the cosmic universe.
The Celestials weren't present when Thanos destroyed half of existence with a snap. Since they aren't born outside of space and time, it is plausible that they succumbed to the same effects that every other living being did. However, that doesn't mean that they didn't have the ability to stop the mad titan. With their immense power and scale, Thanos might have put up a fight, but the Celestials could have easily used their wide range of abilities to defeat him had they been there to stop him.
The upcoming Eternals film looks to be digging deeper into the Celestials and their place in the Marvel cosmic universe. After all, they did create the Eternals by experimenting on early humans. When the new movie is released, viewers will likely learn more about these elusive beings and where they have been hiding. It is entirely possible that they used their powers to pass outside of the known universe or hide in the far reaches of space. Wherever they are, the secrets they guard will undoubtedly change how the world views the MCU forever. Until then, audiences will have to wait and see what the future holds.