While Darth Vader only had a couple of scenes in Rogue One: A Star Wars Story, he had an incredible impact on the movie. The most popular villain in film history pulled the strings behind the decisions of the movie's main villain - Orson Krennic - as well as brought out some of the better scenes in Star Wars canon.
The film referrenced Mustafar - the planet in which Anakin and Obi-Wan had their epic battle at the end of Revenge Of The Sith. The castle in which Vader was residing when Krennic visited him was build on the very planet where Anakin lost his limbs to his former master.
What was referrenced, however, is what Vader had been doing in the years since Episode III. He was seen in some sort of chamber when his lair was revealed, but some new concept art suggests that his residency had more ties to some technology seen in the original trilogy.
When Luke Skywalker - son of Darth Vader - was recovering from his wounds on Hoth, he was placed in a Bacta Chamber. This chamber helped rejuvinate Luke's health while he rested, and it looks like that's the same medical treatment Vader has been undergoing on Mustafar.
Darth Vader may have never recovered from his missing limbs, but perhaps the chamber treatment helped to keep him as strong as he was.
MORE STAR WARS NEWS: Rogue One: A Star Wars Story Five Best Moments | How The Force Changed in Rogue One: A Star Wars Story | Cut Footage From Original Star Wars Used In Rogue One | Rogue One Scores One Of The Biggest Opening Box Office Weekends Ever | Who are the Characters in Rogue One: A Star Wars Story? | Why Darth Vader's Costume Changed for Rogue One