The D'Bari are the main antagonistic faction of the 2019 X-Men film Dark Phoenix. They are a race of shapeshifting aliens led by Vuk to take over the Earth.
Losing Their Home Planet
The D'Bari started out as a peaceful race living on their home planet. However, it wasn't until an unimaginable destructive cosmic entity (known as the Phoenix) wandered across the universe, and later used its powers to destroy the D'Bari's planet, leaving only Vuk and many few D'Bari as survivors. Because of this event, the D'Bari vowed to get revenge on the Phoenix and find a new home planet so that they can replenish back to their former glory.
Tracking Down the Phoenix
In 1992, the D'Bari traveled to Earth, where they used their shape-shifting abilities to take on human disguises; even Vuk takes the form of a young tall and white-haired woman named Margaret Smith that she briefly killed; she would later kill Margaret's husband by making his heart stop beating and allowed her posse to kill the party guests and Margaret's dog Luna. Vuk soon learns that the young mutant Jean Grey absorbed the Phoenix into herself after the X-Men's previous mission to save several astronauts and it also caused her to accidentally killed the mutant Mystique and several police officers.
Deciding that Jean might be a perfect tool to create a new world for the D'Bari, Vuk tracks down and confronts Jean's father John of Jean's whereabouts, but when he refused to cooperate, Vuk kills him. Eventually, Vuk meets Jean in person and tells her about the history of the Phoenix, convincing her to use her powers for her own use and abandon whatever beliefs of morality to achieve it.
When Magneto and the Brotherhood of Mutants conspired to kill Jean in New York City for trying to kill innocent soldiers in their island Genosha, Professor Xavier and the X-Men arrive to stop them. Magneto was able to make his way to confront Jean, but thanks to Vuk's guidance, Jean was able to overpower him. However, Xavier uses his mind-reading abilities to let Jean read his thoughts about why he repressed her memories, which drove her into asking Vuk in taking away the powers. Vuk eagerly does so, but not before she tells Jean that doing so will also deprive Jean of her life, as Vuk intends to use the Phoenix power to destroy all life on Earth so that she can create a new haven for the D'Bari race there. Fortunately, Xavier and Scott manage to stop Vuk from draining most the Phoenix power, but several soldiers (sent by the U.S. government) arrive to arrest both the X-Men and the Brotherhood (including Xavier, Magneto and Jean).
Final Battle and Death
With all the captive mutants boarding on a train to a mutant containment facility, Vuk leads Jones and their D-Bari soldiers to attack the train, killing many of the human soldiers. This forced the surviving soldiers to release the mutants and let them battle against Jones and the D-Bari soldiers. Though Jones and most of the D'Bari soldiers are finished off to their deaths, Vuk (showing no concern over the loss of her soldiers) manages to use her powers (fueled by some of the Phoenix power that she absorbed) to defeat all the mutants (including Xavier and Magneto). However, Xavier helps Jean in gaining control of her Phoenix power, allowing herself to finish off the remaining D'Bari soldiers. Jean then takes Vuk into outer space, where she uses the Phoenix power to disintegrate Vuk to her death for good.