If there are two tentpoles in my fandom, they are Ravenloft and Star Wars. And yet, I don't feel any desire to cross the streams there. Not to yuck the yum or anything, but just honestly answering the question:
How would you do it?
I wouldn't.
- Peradur, I am your father.**
** Yes, I'm aware Vader never says "Luke, I am your father."
I mean, there are elements of SW that would fit right in... the cave on Dagobah for example. I almost said Vader's the perfect darklord, but then I thought more about it and realized that he is eventually redeemed, which kind of disqualifies him. Palpatine then would seem more darklord-worthy, since he
doens't do a face turn ever, but there's not a lot of empathy there. We see his rise to power, but never really see his fall to the dark side or why he joined the Sith. (If it's covered in the
Darth Plagueis book, I'm not aware, as I haven't read it.) While he's still masquerading as good in Episode I, he's already Darth Sidious on the DL. As much as I love him as a cackling BBEG, if I saw him presented as a darklord without any prior knowledge, I'd call him as one-note as say Meredoth (the canon one, not the excellent revamp in the FoS NS Gaz). So neither of them really fit. You'd have to go deeper into the EU - sorry, I mean "Legends" or the ancillary series to find a good darklord, and even then I'm struggling to identify one.
Ravenloft is a lot about choices made, flawed heroes, irredeemable yet sympathetic villains, and also about survival in the face of despair. SW is more often about destiny (i.e the
lack of choices) and the ideal hero's journey, archetypal villains without humanity, but also about hope and redemption. It's tough on a fundamental level to mesh them.