The Darth Vader that will appear in Rogue One: A Star Wars Story won't be the Darth Vader that fans remember from the original trilogy, nor will he be a newcomer to the Sith side, like Anakin Skywalker is at the end of Episode III: Revenge of the Sith.
Warning: This post will contain small spoilers for Vader's role in Rogue One. if you're trying to go in blind, it might be best to stop reading now.
Kathleen Kennedy, Lucasfilm president, told Entertainment Weekly a few key details about Vader's return to the Star Wars universe. James Earl Jones, 85, will reprise his role as the voice of Vader while a new army of young actors walk around in the famous suit. Jones has been voicing Vader on Disney XD's Star Wars: Rebels, but other actors have lent their talents to game and cartoon properties, imitating the voice Jones made famous in 1977.
Kennedy said that while Vader will be used sparingly on screen, he will appear in one of the most crucial moments of the film. As it stands, Rogue One takes place approximately 19 years after the events of Revenge of the Sith, and Darth Vader still isn't the menacing force that he eventually becomes in A New Hope. Instead, Vader is still trying to prove himself, and he'll stand opposite Ben Mendelsohn's Director Orson Krennic, the film's main villain, to do just that.
Krennic and Vader are by no means friends in the film, and are just barely civil to one another. Krennic is still operating under the watch of Emperor Palpatine and thinks that Vader's volatility is a dangerous presence on their side. It's because of Vader's behavior, however, that he's regarded with high praise from Palpatine and is seen as one of the main enforcers on the Sith side.
Just how much Vader will be involved with Jyn Erso, played by Felicity Jones, and the Rebellion is still unknown. Rogue One: A Star Wars Story is set to be released Dec. 16.