Why did Nihilus need Sion's help against Traya?
Just something I've long wondered.
https://www.youtube.com/watch?v=tlgUFQXbXcM
Here are some quotes:
"But Traya underestimates her disciples' depravity. They turn on her and drain her Force powers."
-- KotOR CG
"Sion learns much from the shrew, but grows frustrated with her abstract teachings. He conspires with Darth Nihilus to strip her powers and eventually severs Traya's hand."
-- KotOR CG
"Ousting Traya with Sion's help, Nihilus binges on the Force, nearly extinguishing the Jedi forever at Katarr."
-- KotOR CG
At the end of the day, just about everybody reckons that Nihilus is vastly more powerful than Traya by this point. So why does he need or want Sion's help? He doesn't need backup if he's vastly more powerful than Traya, since he might as well oust Traya by himself and become the undisputed ruler of the Sith Triumvirate - Sion can't possibly challenge him on his own. And Sith don't form alliances unless it's absolutely necessary - especially Nihilus.
For that matter, why would he wait until he was vastly more powerful than Traya to oust her? The nature of Sith is to claim the highest position as soon as you become more powerful than the top Sith. Nihilus was also impatient with Traya because she was denying him the freedom to sate his own hunger. I don't think anybody here would accept the idea that Nihilus actually needed Sion to help him against Traya (ie. Traya's still a bit more powerful than him at this point), but without that explanation, how do you explain Nihilus' need for Sion's aid?