Darth Krayt is non canon. So is Sion. There can only be two Sith at a time; one master, and one apprentice, and Krayt has several Sith underlings while Sion is one of three Sith Lords (masters) who have hundreds of minions. Obviously both go against what George LucasYoda say about the Sith. And anyone who says Yoda is not omniscient speaks poorly. And is a butt.
(I didn't like this thread to begin with.)