Marvel’s Eternals goes deeper into the cosmic lore of the MCU than ever before. Though we have met the Celestials in prior movies, this one fully explores the origins, powers and purpose in the universe. And, as happens sometimes with the franchise, it slightly conflicts with what’s come before. For instance, Guardians of the Galaxy Vol. 2‘s Ego the Living Planet is a Celestial, and yet he seems to be a totally different being from those we meet in Eternals.
But this compelling fan theory offers a very persuasive take on how Ego could fit in with the new information we’ve learned about the Celestials. As u/Xygnux pointed out on the r/MarvelStudios subreddit, Ego’s planet form doesn’t resemble Arishem and Tiamut from Eternals and yet their shared MO – planting their seeds on other worlds – proves they are the same species. So the theory goes that Ego is a lost Celestial embryo left to fend for itself:
“Imagine a Celestial embryo early in its gestation inside a planet its parent put it into. Except for its brain, most of it was still not formed. But some disaster that its babysitting Eternals failed to stop destroyed the entire planet. The parent Celestial assumed that the embryo must be dead.”
The theorist goes on to suggest that this embryo, which was just a brain and central nervous system, survived and was “prematurely awakened… with no idea where it came from or what it is.” This fits with Ego’s speech about how he was born “utterly and entirely alone”. Over the eons, however, he learned to use his Celestial powers and created his planetary shell around him.
At some later date, Ego encountered others of his kind and learned that he was a Celestial. He “became angry” and “hated his people for abandoning him and failing to save him.” Envious of his unborn siblings who were fated to gestate into full-grown Celestials, Ego cooked up the plan for his Expansion: he would plant his seeds on planets that were housing other Celestials, turn them all into “beings just like himself” and “even replace their minds with his own.”
Several other fans in the comments to the original post voice their support for this theory, saying that it’s now become part of their own head-canons. It’s definitely a smart recontextualizing of Ego’s origins and scheming and helps joins the dots between Guardians 2 and Eternals. Let us know what you think of this fan theory in the comments.