The Earth — the planet itself — serves as an egg to an unborn Celestial, and the Earth will be destroyed when it hatches. .
In this broad earth of ours,.The passage from "Song of the Universal," as it's used in "Eternals" is not only literal — there is literally a seed perfection nestled in the broad Earth — but a direct clue as to what is happening with the Earth.
The Whitman poem — recited by a character named Whitman, hmm — was not the only hint about the Celestials that Zhao dropped in either.In the Babylon sequences of "Eternals," the character of Makkari (Lauren Ridloff) makes mention of The Emerald Tablet.
The Earth carried it in her belly, and the Wind nourished it in her belly,It ascends from the earth to the heaven
"The Earth carried it in her belly?" "It ascends from the earth to the heaven and becomes ruler?" These are all pretty open allusions to a powerful space deity nesting in the heart of the EarthWhether or not ancient humanity knew about Arishem's plan to use the Earth as an egg for another Celestial is unclear; perhaps the author of The Emerald Tablet somehow knew about the Celestial gestating at the planet's core