Did you know that the rebel base on Yavin IV in A New Hope was originally a Sith temple? It was built by the ancient Sith Lord Exar Kun. He was of the previous generation before the Mandalorian Wars and the rise of Darth Revan. The spirit of Exar Kun still haunted the building even during the movie era.
In KOTOR 2 you get a starport visa to go to Onderon, where a schism is happeninf because General Vaklu wants Onderon to secede from the Republic but Queen Talia wants to stay in the Republic and the two factions are in a tense relationship. Also General Vaklu is secretly in contact with the Sith.