Celestials are cosmic entities that date back to the first known existing universe. These so-called “space gods” visit other planets to assess their lifeforms, judging which are worthy and which are inferior. From the baseline species of the planet, Eternals and their evil counterparts, Deviants, are formed.
Thus, one million years ago, Celestials created 100 Eternals for Earth. And then the Celestials vanished — though if the Eternals trailers are any indication, these destiny shapers are still calling a lot of shots.