Darth Vader experimented with resurrection. Before the battle with Luke, he managed to resurrect PadmΓ©. After death, some of Darth Vader's power passed to her. The world has changed for her and she decided to continue the work of her beloved.
Finally, I finished painting all the interesting places. ;)
By the way, I forgot to say that there is a whole theory that the Sith Lord is Jar Jar Binks. If you haven't heard, google it, it's interesting.