Marvel had no comment on who Jolie might play, but given that she's the first actor to be cast, it seems likely that she's up for the transmutation-powered Sersi. Jolie also looks a great deal like many artists' depiction of the character. But who is Sersi? And what does Jolie's casting tell us about the film?

Unlike the previous films that have made up the Marvel Cinematic Universe, The Eternals is based around largely unknown entities, even for most comic book readers. This unknown quality plus the fact that Marvel Comics hasn't made much effort in reprinting Kirby's series or key appearances of the characters (yet), adds a level of excitement and novelty to Zhao's feature. As a property that's more situated in the realm of sci-fi and fantasy than superhero yarns, learning about the Eternals is akin to taking a deep-dive into J.R.R. Tolkien's Middle-earth history or George R.R. Martin's Westeros and Essos. While the Guardians of the Galaxy were mostly unknown to most audiences before 2014, the Eternals are even more of a deep-dive into the Marvel Universe. When it comes to the Celestials, the Eternals and their evil counterparts the Deviants (Thanos' race), this is heavy Marvel mythology, the building blocks of the universe, and far more complex than anything we've seen Marvel Studios adapt thus far.

Casting Jolie in a film such as this is a way for Marvel to ground the audience in a complicated mythology with a familiar face. But it's also a signal that if an actress on this level of influence, one who has largely focused on directing and producing of late, is interested, then it must be something special.

Marvel Studios, with a few exceptions, has long played the game of star-making when it comes to leading roles, taking talented actors and actresses known from television and award-season breakouts and making them household names or reviving the public's perception of them. There's been a certain tier of actors who first broke box office records and sold magazine covers in the '90s — Tom Cruise, Brad Pitt, Leonardo DiCaprio, Denzel Washington, Tom Hanks, Julia Roberts and Jolie — who have somehow managed to avoid being in a superhero film. But it now seems as though everyone must do at least one. Despite being a favorite for numerous superhero roles since the '90s and being an early rumored choice to direct Captain Marvel, Jolie has stayed away from superhero movies. Sure, she played Lara Croft twice and starred in the comic adaptation of Wanted (2008), which stripped away the superhero element of Mark Millar's comic, and she went all-in on the costumed villainess in Maleficent (2014) and its upcoming sequel. But she's never played a true superhero before.

Yet Sersi, if speculation is indeed correct, seems like a fitting choice for Jolie. Not only does the role provide her with the opportunity to work with Zhao, whose film The Rider (2017) makes the filmmakers seem like kindred spirits, but Sersi reflects many of Jolie's own acting choices and interests.

Created by Jack Kirby, Sersi first appeared in Strange Tales No. 109 (1963), with the name spelled "Circe," then later as Sersi in The Eternals No. 3 (1976). The distinction in spelling highlights a very important aspect of The Eternals' comic book history. While Greek gods and goddesses exist in the Marvel Universe, they would often let the Olympia-based Eternals represent their physical forms for the humans on Earth, hence many of the Eternals sharing names similar to their Greek counterparts. This distinction sounds like something the MCU will merge and just make the Eternals the inspiration for the Greek Pantheon, like the Asgardians were the basis for the Norse Gods. The comics have already done some of this synthesizing. Sersi inspired the poet Homer, who included her under the name Circe in The Odyssey in which she turned men into swine. Because of her powers to manipulate matter and rearrange molecular structures, she was often seen as a witch rather than a result of alien experimentation, allowing her to move across comic book genres.

While most of the Eternals eventually returned to the cosmos in search of their larger destiny, Sersi remained on Earth, fascinated with its people and customs. She involved herself in key moments in history, lived in ancient Rome and Camelot, fought alongside Thor and the Vikings in the god's youth and later joined the Avengers.

Having lived for millennia, Sersi has taken on many roles on Earth and has changed her personality as she's seen fit, taking the most out of her immortal existence. This worldliness and interest in alleviating human conflict and suffering falls in line with Jolie's own humanitarian and conservation efforts. As the line between actors and the superheroes they play grows increasingly thin (see Chris Evans' political interests, and Gal Gadot and Brie Larson's movement for women in film), Sersi may be a way for Jolie to get her message out to a wider audience, and exhibit godlike powers while doing it.

It's impossible to capture the massive potential and mythology of The Eternals through one character and casting choice. But Jolie's involvement at least gives us a better idea of what's coming down the road post-Avengers: Endgame. Marvel Studios boss Kevin Feige has promised a very different MCU after April 26, and if Jolie's casting and Sersi's eons-spanning history and mythology is any indication, Marvel's storytelling and casting is only growing in ambition.