The Celestials are immensely powerful beings featured in the Marvel Comics universe, considered by some to be villains (confirmed as such in a few official works, where they have fought heroes and villains alike, they are greatly feared even by a being of Galactus’ might – although in others Galactus has engaged.

Reality: First Cosmos, Multiverse

Body Type: Humanoid

Special Adaptations: Armor

In the great void, emptiness reigns. Save for the unknowable, unexplicable life that somehow exists without homeland, without sustenance. Voicelessly uttering secrets that would destroy our sanity. The Celestials. Created of the First Firmament. Witnesses to the birth of all. They watch each civilization, from primordial to transcendent. They test. They prod. They observe. And then, as voiced by the most coldly impassionate of their member, Arishem…they pass judgment.
—Narrator

Celestials are powerful cosmic beings created by the First Firmament. Within Greek mythology, Uranus was the primordial sky god, who was ultimately succeeded by Zeus, who ruled the celestial realm atop Mount Olympus. The Celestials rebelled against their creator and Aspirant counterparts in a war that shattered the first universe into the first multiverse. The Celestials wield the Power Cosmic and their abilities are almost limitless. Even though they’re some of the most incredibly powerful entities ever to exist, they’re not the most powerful. The Celestials are involved in the creation of new universes, including that of the Prime Marvel Universe.