Celestials are powerful cosmic beings created by the First Firmament. The Celestials rebelled against their creator and Aspirant counterparts in a war that shattered the first universe into the first multiverse. The Celestials are involved in the creation of new universes, including that of the Prime Marvel Universe.

The Celestials first appear in The Eternals #2 in 1976. Their creator Jack Kirby described them as ancient, towering beings, whose experiments with early hominids resulted in the creation of both the Eternals and the Deviant races.