While Fox was perfectly fine spoiling Dark Phoenix’s major death in early advertisements, the true identity of Jessica Chastain’s alien character was kept conspicuously hush in the weeks leading up to the film’s premiere. Though an explanation for the codename she was referred to by the studio (“Smith”) is never explained in the film itself, a brief exchange is packed with just enough information about Chastain’s character to reveal who they are and how they fit into the larger Dark Phoenix Saga.
It would be logical to assume that, being an alien in an X-Men story about the Phoenix, Chastain might end up being Lilandra Neramani, Majestrix of the Shi’ar Empire and former lover of Charles Xavier. Surprisingly? She’s not.
Marvel’s Dark Phoenix Saga, which the movie is based on, is dense and features a large cast of characters that Fox’s X-Men cinematic universe really couldn’t accommodate. But rather than completely passing on its chance to finally pit the X-Men against proper aliens, Dark Phoenix instead cherry-picked a notable (yet small) group of characters to highlight that have an important canonical connection to the Phoenix Force.
Early into Dark Phoenix, a number of huge, glowing objects crash to Earth near a wooded area. A human woman (played by Chastain) at a dinner party that’s particularly close to an impact site wanders off to see what’s up when her dog begins barking nonstop outside. What the woman finds is a gathering of shadowy, humanoid creatures, one of whom wastes no time in killing her, assuming her form through some very Skrull-like shapeshifting, and then returning to the party where the remaining humans are murdered as well. It isn’t until all of the aliens have adopted human guises that they begin discussing their plan with one another in their native tongue, and it becomes clear that they aren’t Shi’ar, but rather the surviving members of the D’Bari race, and Chastain’s D’Bari name is “Vuk.”
In Marvel’s comics, the D’Bari make their first appearance in The Avengers #4. Captain America discovers that a stranded D’Bari named Vuk has been tasked by Namor the Submariner to turn the Avengers into stone in order to regain access to his crashed ship, which has sunken into Atlantean waters. After the Avengers help Vuk sort things out, the alien leaves the planet for some time, but the D’Bari become important figures in the larger universe during the Dark Phoenix Saga after a Phoenix-empowered Jean Grey consumes the energy of a star at the center of a system of 11 planets where the D’Bari live. By causing the star to go supernova, Jean inadvertently kills billions.
While Jean’s actions snuff out the lives of five billion D’Bari, a small number of people who were not within the doomed star system at the moments of the Phoenix’s arrival have popped up in a variety of Marvel’s other cosmic comics. But Jean’s turn to genocide is ultimately what puts the Dark Phoenix on the Shi’ar’s radar, prompting the aliens to insist upon destroying Jean, much to the X-Men’s dismay.
In Dark Phoenix, Vuk explains to Jean (Sophie Turner) that her world was consumed by the destructive, fiery power jetting through deep space. But in this telling, the Phoenix isn’t exactly a sentient fire bird, it’s an energy cloud that just blows things up as it crashes through them in an effect that reminds you of Fantastic Four: Rise of the Silver Surfer’s take on Galactus. It’s interesting that in this film version, the Phoenix Force itself is wholly responsible for the massive loss of life and Jean is fully innocent of any wrongdoing. As it turns out, the thing that makes her a person of interest to the D’Bari is that, for whatever reason, the Phoenix couldn’t destroy Jean.
Curiously, Dark Phoenix’s third act boils down to Vuk revealing herself to have ulterior motives: to steal the Phoenix Force for herself in order to use its power to remake the D’Bari homeworld. While there’s a lovely kind of poetry to the way Dark Phoenix reworks Jean’s connection to the D’Bari—turning them into a people looking to be reborn—the plot doesn’t exactly make much sense, considering that if Vuk could absorb the Phoenix on her own, she should have just done so before it bonded with Jean. That’s the kind of minor plot hole that keeps the D’Bari’s plan from seeming like it was very well thought-out, which, if anything, is the reason they don’t ultimately succeed.