Marvel's Eternals trailer revealed the sheer power of the Celestials - but why did the Guardians of the Galaxy films render these space gods extinct? Created by the legendary Jack Kirby back in 1976, the Celestials are a race of space gods who visited Earth at the dawn of time. These beings were old when the universe was young, and they were responsible for seeding life on countless worlds across the galaxy. They return infrequently to judge the worlds they seeded, to decide whether the species that flourish on these planets are worthy of continued existence.

The Celestials have been a part of MCU lore since 2014, but Marvel's upcoming Eternals movie promises to explore them in detail. It makes sense for the Celestials to have a significant presence in this movie because in the comics they were the ones who created both the Eternals and their rivals the Deviants, led by Warlord Kro. The MCU is switching things up - all evidence suggests that the Eternals have been sent to Earth to protect humanity, rather than simply being an evolutionary offshoot of the human race - but the Celestials still seem to be the ones who have assigned them to this task.

Related: Eternals Final Trailer Breakdown: 31 Reveals

But why haven't the Celestials been seen in the MCU's present? Surprisingly, their apparent absence has already been set up (although not explained) in the Guardians of the Galaxy films.

How Guardians Of The Galaxy Setup Eternals' Celestials (Knowhere & Eson)

Celestial in Guardians of the Galaxy

James Gunn's Guardians of the Galaxy subtly suggested the Celestials were part of the MCU's past - but not the present. In one key scene, the Collector showed footage of one of the Celestials, Eson the Searcher, brandishing the Power Stone and using it to judge an entire world. But it was striking that the images were supposed to be from the ancient past, and the Power Stone had been long lost - concealed on Morag, where Quill enters the MCU, for millennia. The shocked reactions of the soon-to-be Guardians of the Galaxy seemed to confirm none of them had ever heard of a being like Eson, with Peter Quill speaking for everybody in his own inimitable way when he observed, "There's a little pee coming out of me right now."

Meanwhile, the film also introduced viewers to Knowhere. This mining colony is situated in the severed head of a Celestial, again confirming the size and power of this ancient race - and suggesting they were nothing but a distant memory to the galaxy. In the comics, this Celestial was slain by Knull, the God of the Symbiotes, using the Necrosword as part of his campaign against light and life.

Guardians Of The Galaxy's Celestial Power Reveals & Ego's Death

Ego talking to the Guardians of the Galaxy.

Guardians of the Galaxy Vol. 2 further developed the MCU's Celestial lore when it introduced the real villain, Ego, who considered himself the last of the Celestials. "I don’t know where I came from exactly," Ego explained to the Guardians. "First thing I remember is flickering… adrift in the cosmos utterly… and entirely alone." According to Ego, he searched the cosmos for more of his kind and drew a blank; this drove Ego mad, and he focused on absorbing the universe into himself to bring unity and cohesion to all things.

Related: MCU Theory: Eternals Trailer Shows The Origin Of Mutants

The sequel revealed a great deal about Celestials. It seems these cosmic beings are composed of some undefined energy, "living light" that lies at the core of their beings. The Celestials possess the power to manipulate matter on a molecular level, and Ego initially created an entire planet - and subsequently avatars for his being through which he could explore the universe. Presumably, all the forms seen before - Eson the Searcher and the severed head of a dead Celestial that is Knowhere - were forms some Celestials created to contain their living light, instead of worlds. Interestingly, Ego did suggest if he strayed too far from his "living light" for too long he would die; "If I don’t return regularly to my planet," he explained, "and the light within it… this form will wither and perish."

Why Guardians Of The Galaxy Suggested The Celestials Were Gone

An unidentified Celestial creates an energy ball in his hands in Marvel's Eternals.

But why did Marvel initially choose to reveal the Celestials had been rendered extinct? It's important to remember that, back in 2014, Marvel was still wary of diving too deep into the strange and supernatural; thus the idea of introducing an entire race of space gods would have been a little too fantastical for the studio back then (even factoring in director James Gunn choosing to tell stories featuring a talking tree and a walking raccoon). There is a sense in which the Celestial reveals in Guardians of the Galaxy Vol. 2 were quite organic, because the Celestials were already supposed to be capable of wielding the Infinity Stones - and something about Peter Quill's lineage meant he was as well. It was actually logical for Quill to be a part-Celestial, and Ego's story flowed from that.

Oddly enough, Marvel's decision to remove the Celestials from the MCU's present helped the studio redesign Thanos. In the comics, Thanos' evil is derived from his devotion to the avatar of Death, but the MCU's Thanos is nothing like the comics; he's focused on saving the universe in some insane concept of "balance." The language of balance is traditionally associated with the Celestials rather than with Thanos, because they consider themselves responsible for maintaining the equilibrium of all creation. Thanos would have felt a little repetitive had the Celestials still been a force to be reckoned with in the MCU.

How  The Celestials Could Have Been Killed Off

An aerial shot of Sakaar during the day

Of course, this raises an obvious question; what exactly happened to the Celestials? There are hints this ancient race was wiped out in some sort of cosmic battle, whether in a civil war or because various civilizations decided they were tired of these space gods turning up to judge them every now and again. Knowhere is, after all, part of a Celestial corpse; and according to the Marvel Studios Visual Dictionary, the planet Sakaar was littered with the remains of Celestial bodies (Thor: Ragnarok even featured a spaceship associated with the Celestials, suggesting one of the Celestials' vessels had crashed on Sakaar as well). So it looks as though the Celestials were rendered extinct, rather than passing gently into the night.

Related: Eternals Can Show Just How Slow MCU's Quicksilver Was

The most likely explanation for the Celestials' extinction is that the Infinity Stones were used against them. The Collector alluded to beings long ago using the Power Stone for an unspecified purpose; that could well have been the moment the Celestials were wiped out, with the races they had judged finding them wanting. They may well have simply been obliterated. When the living light within them is exposed they can be killed, as seen in Guardians of the Galaxy Vol. 2. Instead, they could have been banished to another plane of existence.

How The Celestials Could Return In Eternals

Eternals Emergence Hulk Snap

According to the second Eternals trailer, the release of cosmic energy associated with Hulk's snap in Avengers: Endgame has provided sufficient power to trigger something called an "Emergence". They may have vanished millennia ago, but it's quite likely the Celestials will return in Eternals.  While it is possible this is somehow associated with the Deviants, it is more likely the Deviants are simply attempting to take advantage of the chaos caused by the Emergence - and that this mysterious event is somehow associated with the Celestials. That is signified by the idea the Eternals have seven days to save the world, seven being the number of God in Judeo-Christian traditions.

It's difficult to say how the Celestials will return, simply because Marvel is yet to reveal how they were defeated in the first place. If the Celestials were banished to another dimension, then the Emergence, caused by the power of Hulk's snap, could be the moment when they tear through the fabric of reality and enter this plane of existence. Alternatively, if they were wiped out then it could be there is still a way for them to return; in Marvel's Earth X series, various superheroes learned a Celestial seed lay at the heart of the Earth itself. Marvel could do exactly the same here, revealing the Celestials' creation of galaxies and worlds was part of their own life-cycle, and that the energy from the Hulk's snap has matured this. That would certainly fit with the shots of energy rippling across the Earth's surface.

Whatever the case may be, though, it does seem as though the Celestials are returning to the MCU. If that is indeed the case, then the Avengers' heroism has had unexpected consequences - transforming the MCU's cosmic status quo, with Eternals revealing just how dramatic those changes may be.

More: Eternals Just Teased Black Panther 2's Villain Origin - Theory Explained

Key Release Dates