Loftwings and Demons

We Sith are an unseen opposition, Tenebrous had told his young apprentice. A phantom menace. Where the Sith once wore armor, we now wear cloaks. But the Force works through us all the more powerfully in our invisibility. For the present, the more covert we remain, the more influence we can have. Our revenge will be achieved not through subjugation but by contagion.

--from the Darth Plagueis novel by James Luceno