Avengers: Endgame may have ended the Infinity Saga but the Marvel Cinematic Universe is far from over. Marvel Studio's Phase Four will introduce a slew of new characters into the universe starting with Eternals. In actuality, these immortal, ancient beings have been in the MCU, all along but soon they'll have to come together to defend Earth from their sworn enemy, the Deviants.

Here's what we know so far about Eternals, including the trailer, plot synopsis, release date and cast.

EDITOR'S NOTE: Updated Sept. 26, 2021, to include actor Dan Stevens' cryptic comment seemingly confirming his role in Marvel's Eternals.

RELATED: Marvel's Eternals Teaser Trailer's Biggest Moments & Key Characters

Marvel's Eternals Teaser Trailer

Released on May 24, 2021, the first official teaser trailer for Eternals depicts the group arriving on Earth during ancient times and settling down with the locals. As Skeeter Davis' "The End of the World" plays in the background, Salma Hayek's Ajak explains in voice-over that they've helped humanity advance but never interfered until now. The trailer shows the Eternals living amongst humanity throughout the years. In one shot, Sersi bonds with the locals and helps them with some farming. Another shot shows a group of people who appear to be kneeling to the Eternals, perhaps as a sign of respect or even worship. There's also an extended shot of the group in front of the Ishtar Gate of Babylon and at one point, they all use their powers together, possibly to form a Uni-Mind. Fans can also catch a quick glimpse of Kit Harington's Dane Whitman sanding with Sersi.

Throughout the trailer, individual Eternals also get to show off their abilities and personalities. Thena spars in an area surrounded by turquoise sheets of fabric. Makkari speed-reads through piles of books and saves a girl from a falling pillar. Sersi wanders through city streets and is also seen with Ikaris throughout different eras. Sprite sings in a private jet with a bar but looks worried in another shot where she's surrounded by a volcanic backdrop. Indeed, a volcano can later be seen erupting in the trailer. Ajak comforts Phastos and both are shown using their powers on different occasions. Kinko performs a Bollywood number. Finally, Druig is seen walking into what looks like some sort of commune in a forest, which also serves as the setting for a fight later on.

The trailer ends with a group of Eternals eating together in modern times. Ajak, Makkari, Phastos and Druig are absent. Ikaris thanks Gilgamesh for the food and Sprite asks who the others think will lead the Avengers now that Captain America and Iron Man are gone. Ikaris responds that he could lead them, which makes everyone laugh.

RELATED: The MCU's Most Powerful Character Was Only Seen ONCE - His Return Will Be TERRIFYING

A First Look at Eternals Debuted in Early May 2000

Fans got their first glimpse at Eternals in the video, "Marvel Studios Celebrates The Movies," on May 3, 2021. The short clips show the group standing on a beach, in a forest and in front of the Ishtar Gate of Babylon, as well as individual shots of Ajak, Thena, Sersi and Kinko.

In July 2020, one of the stars of the film, Ma Dong-seok, also known as Don Lee, may have leaked a teaser poster for the film on Instagram. The poster appears to show the Eternals standing together with several large lights behind them. Some fans believe these could be portals while others are speculating that it may be the face of Eson the Searcher, a Celestial who appeared briefly in Guardians of the Galaxy. This would be fitting since the Eternals were created by the Celestials.

RELATED: Why MCU's The Eternals Could Reveal A Key Namor Location - Atlantis

Eternals' Final Trailer

On August 19, 2021, a final trailer for Eternals was released, revealing more plot details and tie-ins to the larger MCU. It begins with Ajak coming to visit Ikaris. She explains that the return of half the universe's population in Avengers: Endgame has led to the start of an "emergence." As she speaks, something is shown falling to Earth, with its impact sending ripples across land and sea. Ikaris asks how long they have, and Ajak responds with "Seven days."

The trailer then cuts to another scene, which could be showing the Eternals' creation. A large, red figure stands in the center of the Eternals, and a golden light floats toward a motionless Ajak. When it reaches her, her eyes open with a flicker of gold. In voice-over, Sersi recounts how they "came to Earth 7,000 years ago to protect humans from the Deviants." At this point, viewers get their first glimpse at the Eternals' sworn enemy, as one monstrous-looking Deviant crawls onto shore towards a young child. Ikaris is then shown blasting it with energy beams as the creature spreads its wings. The story shifts to a conversation between Dane Whitman and Sersi, with the latter explaining that the reason they've never interfered with humanity before is that they were instructed to only do so if the Deviants were involved. Dane asks "By who?" and the trailer cuts to a shot of one of their creators, a Celestial revealed in merchandise to be Arishem.

The Eternals are depicted interacting with humans and fighting the Deviants over the years and coming together in the present day. In another notable shot, Thena is restrained by a more humanoid Deviant, who tells her, "You can't protect any of them." In the comics, Thena does have a relationship with a Deviant named Kro. The character has not been confirmed to be appearing in Eternals, but many are now theorizing that this is the live-action version of the warlord.

RELATED: Marvel Just Answered Our Biggest Question About the Eternals

The Official Plot of Eternals

Angelina Jolie in Eternals

Here's the official synopsis for Eternals, released May 24, 2021, with the teaser trailer:

Marvel Studios’ Eternals welcomes an exciting new team of Super Heroes to the Marvel Cinematic Universe. The epic story, spanning thousands of years, features a group of immortal heroes forced out of the shadows to reunite against mankind’s oldest enemy, The Deviants.

Another synopsis was released on August 19, 2021, alongside the final trailer, which reads:

"When monstrous creatures called the Deviants, long thought lost to history, mysteriously return, the Eternals are forced to reunite in order to defend humanity once again."

Eternals director Chloé Zhao recently addressed arguably the biggest question about the film, asked repeatedly since the release of the first trailer: why the Eternals didn't step in to defend Earth against Thanos. “[The audience] will understand why,” Zhao said. "Not only why, but how complicated not interfering made them feel. We explore that. You’ll see that in the film. The Eternals were instructed not to interfere with any human conflict unless Deviants are involved. There’s a reason why that’s the case. And that was the instruction from the prime Celestial Arishem."

Created by Jack Kirby, the Eternals are a race of powerful, practically immortal humanoids. They came into existence long ago when the Celestials, a group of ancient god-like beings, came to Earth and experimented on pre-humans. The Celestials also created the Deviants, a race of intelligent, monstrous-looking humanoids. While the Deviants have hidden underground, the Eternals have lived secretly among humanity for millennia. The two groups have always clashed.

Marvel's Eternals one-sheet

The film will take place after Avengers: Endgame, and will explain what the Eternals have been doing all this time. Since they've been around for thousands of years, they've existed in the MCU from the beginning but have yet to reveal themselves to the world. The Eternals may have stayed out of these conflicts for a reason but some of them could have been secretly helping all along, like the Ancient One in the Battle of New York. While Eternals will focus on the group, Kevin Feige has indicated that Gemma Chan's Sersi will be a sort of main character for the movie.

RELATED: Eternals' Chloe Zhao Fought for Practical Locations Versus Green Screen

Eternals Release Date

Every member of the Eternals arrive during a sunrise with their ship in the background on the movie poster for Eternals

Although Eternals was originally set to be released in November 2020, it has since been pushed back to Nov. 5, 2021, because of the coronavirus (COVID-19) pandemic. Filming wrapped in February 2020, and the movie is now in post-production. While the movie was initially being billed as a theatrical exclusive, Feige recently cast doubt on this. Regardless of how it's released, Disney CEO Bob Chapek insists that they are sticking to the release date.

Eternals Cast & Crew

Eternals group shot, from the Marvel teaser

Eternals is helmed by Oscar-winning director Chloé Zhao (Nomadland, The Rider) with a screenplay by up-and-coming screenwriters Matthew and Ryan Firpo.

Some alterations have been made to the characters' races and genders from the source material. As a result, it features a diverse, star-studded cast with Richard Madden as Ikaris, Kumail Nanjiani as Kingo, Lauren Ridloff as Makkari, Brian Tyree Henry as Phastos, Salma Hayek as Ajak, Lia McHugh as Sprite, Don Lee as Gilgamesh, Angelina Jolie as Thena, Barry Keoghan as Druig, Gemma Chan as Sersi and Kit Harington as Dane Whitman/Black Knight. The film also features Marvel's first openly gay superhero, along with its first deaf superhero.

Actor Dan Stevens, known for his roles in Legion, Downton Abbey and Disney's live-action Beauty and the Beast, seemingly confirmed rumors that he has a secret role in Eternal. Asked by Collider's Steven Weintraub, "What can you say, hypothetically, about any sort of role that you may or may not have in Eternals?," Stevens replied, "Kro comment."

That's presumably a reference to the warlord Kro, who in Marvel Comics is dictator of the Deviants, sworn enemies of the Eternals. Secretly, however, he is an immortal shapeshifter who's more like the Eternals than the Deviants he rules.

This article will be updated as more information becomes available.

KEEP READING: Final Eternals Trailer Ties Into Avengers: Endgame, Teases New Apocalyptic Event