Theory on Nihilus' True Identity
This is just a thought that popped into my head on who Nihilus might be. What if he was Naga Sadow. He fits the description pretty well. He could still be alive since he went to Yavin wasn't it and was in suspended animation for six hundred years then Freedon Nadd woke him up. It's also thought, but never confirmed that Freedon eventually killed Sadow. Keyword. Thought. It has never been confirmed anywhere. Plus, Sadow definatly was powerful enough to be Nihilus and he also lived in a time of lots of accesible Sith knowledge. This is probably all crap though.