Alright folks, can it be possible that this "True Sith Threat" or "Great Evil" as Nightcleaver calls it, is none other than.....
....The Sith'ari that Yuthura spoke of!
She said something along the lines that it's prophesied that when the time is right, the perfect Sith (some sort of higher being) will come and destroy everyone and re-make them greater than before.
Could this Sith'ari be lurking in the Unknown Regions? Is this what Revan went off to fight?
:ph34r:
EDIT: Damn Derro, you beat me to it.