The release of The Marvels (aka Captain Marvel 2) is still far off in the future, and even farther now that Disney has pushed back the release dates for most of their upcoming MCU movies. But this hasn't stopped fans from obsessing over this new entry in Captain Marvel's story and theorizing about what route it could possibly take and what new characters might be introduced. There isn't much information out about the movie yet, only that Iman Vellani's Ms. Marvel and Teyonah Parris's Monica Rambeau will be making appearances, which is exciting for fans who are already (or soon will be) in love with those characters, and it also expands the Captain Marvel universe and cast of characters into its own distinct property.
It was announced in February that actress Zawe Ashton (known for her work inVelvet Buzzsaw and the Broadway play Betrayal) would be joining the cast of The Marvels as a villain, though the specific character was never revealed. The official release date isn't until 2023, so there hasn't been much further news about the movie or what character Ashton will be playing in it. Since there's nothing that Marvel fans love more than theorizing, here are some ideas about the possible role that Ashton will be taking on in The Marvels.
Moonstone
Karla Sofen is one of Captain Marvel's most recognizable villains, and she has ties to both Carol Danvers and Monica Rambeau's iterations of the character. Sofen was a psychiatrist who got a hold of (and fused with) the Moonstone, which is a Kree device that gives its user great power, including superhuman strength and speed, flight, intangibility, and photokinesis (the ability to manipulate light), which allows her to create photon blasts.
Moonstone was a part of various villainous teams in the Marvel pantheon, including the Dark Avengers, the Thunderbolts, and Baron Zemo's Masters of Evil. The Dark Avengers has been hinted at in the MCU, with The Falcon and The Winter Soldier and Black Widow featuring appearances from Valentina Allegra de Fontaine attempting to recruit some more morally ambiguous characters into what fans believe will be a Dark Avengers-style lineup. If this is the plan, it would make sense to introduce Moonstone as the Captain Marvel equivalent on the team, and her ties to both Carol and Monica (who will both be the main players in The Marvels) makes it a likely possibility that this is the role the MCU has planned for Ashton.
Genis-Vell
Though Genis-Vell is typically a male character, it's possible that Ashton could be playing a gender-bent version of the character. Genis-Vell discovers that he is the son of the first Captain Marvel and decides that he should be the one to inherit that legacy. He ends up battling Monica Rambeau (Captain Marvel at the time) for the title. He would eventually be driven mad by Cosmic Awareness giving him more knowledge than he could emotionally handle, which caused him to go on a rampage across the universe to bring "order" upon it.
Though in the MCU timeline, Carol was technically the first to take on the Captain Marvel mantle, the character of Mar-Vell still exists. Ashton could be portraying a female version of Genis-Vell who learns of her mother's sacrifice and decides that she should be the one to carry on the name of Captain Marvel, not Carol or Monica. This movie needs a villain who has a similar or at least a comparable set of powers to Carol and Monica's, and a cosmic character like Genis-Vell would be a good fit.
Deathbird
Deathbird is the heir to the throne of the Shi'ar Empire, which is a race of avian-descended humanoids who are incredibly technologically and militarily advanced, to the point where they conquered every planet in their galaxy (hence the Empire). Deathbird is known for her terrifying lust for power, to the point where even her own people attempted to prevent her from taking the throne. She built her own army and took her birthright by force anyway, which eventually lead to her setting off to conquer other worlds, including Earth (where she met and fought Carol Danvers).
Deathbird would be a huge threat for Carol, Monica, and Kamala to face in The Marvels, and would really set the stakes high. This would also give the MCU a chance to introduce a new alien race to the fold, which could be lots of fun and give them a lot of possibilities to work with in the future.
Rogue
Though Rogue has already made on-screen appearances (being portrayed by Anna Paquin in the X-Men movies), the mutants belong to Disney now, and it's likely that the MCU will start to bring in their own new versions of the characters to the universe they've established so far. Rogue is known primarily as an X-Men character and is typically a hero in the comics, but she has her ties to Captain Marvel as an antagonist as well.
Rogue initially began her journey as part of Mystique's Brotherhood of Evil Mutants, and in a fight with Carol Danvers, Rogue's mutant powers caused her to absorb Carol's powers and memories. Because Rogue was so inexperienced with her mutant abilities, using them caused her to also absorb part of Carol's psyche, which led to Rogue having a part of Carol's mind inside her own for years. This eventually led to her joining the X-Men, and it could be a really interesting way to introduce the character and could help introduce the idea of mutants as a whole to the MCU. However, would Marvel go for the amnesia route again with Carol when that was such a huge part of her first movie? Probably not, but maybe they could find a workaround, or tweak the effects of Rogue's powers a bit. Either way, Ashton entering the MCU as Rogue is definitely still a possibility.