Originally Posted by Zerimar Nyliram
And before anyone says the "true Sith" were Bioware's idea, we've talked about this before: the line that appears in that loading screen in the first game was a throw-away line without much thought behind it, and referred to something entirely different (namely, the Sith species that the exiled Dark Jedi conquered).
Just some food for thought: in one of the early conversations with Canderous, you can get him to mention that the Mandalorians attacked the Republic because the Sith thought it was a good idea. I doubt he was talking about the Exar Kun & Friends Sith, since the Mandalorian Wars started ~30 years after they were wiped out (and the Mandos already participated in that anyway), and that seems to imply they met the Unknown Regions Sith, possibly when they were melting non-Republic faces across the galaxy.
Like I said, it's an early conversation, you can get it on Dantooine with no major effort required if you want to hear it yourself.