Fashk of course. "Head-thing talk! Head-thing talk, learn power." "Talk power! Talk rock-den!" He's already got a power base on Tython as well. The Jedi don't stand a chance.

The Sith Empire is not a true military society. It's not rational, the very basis of the Sith Code is irrationality - passion doesn't usually lead to clear rational choices. It's leadership has no interest in the good of the empire, they are only concerned with their own personal long term struggles for power. The Empire's reasons for signing the Treaty of Coruscant have nothing to do with military advantages or disadvantages but the insane whims of their emperor. The slave revolts on Dromund Kaas aren't due to a lack of power or control, but are a direct manipulation by some Sith to undermine other Sith.

It also plays into the story a bit when you learn Darth Thanaton never chooses his apprentices from slaves as he's supposedly an arch traditionalist, whereas Zash is not.

Exactly.

Well, ultimately we know the Sith Empire does fail. Now when that occurs is open ended, but obviously sometime before the rise of the New Sith Empire c. 2000 BBY (founded by Darth Ruin, which will also eventually be destroyed circa 1000 BBY, followed by the rise of Darth Bane and the rule of two). As far as I know there's a pretty big timeline/lore gap between Vitiate's Sith Empire (the one for the game) and the one founded by Darth Ruin. I suspect at some point in the timeline the emperor dies or is killed, and then you have a bunch of warring Sith "fiefdoms" until the rise of Darth Ruin, as the emperor's strength appears to be the only thing keeping the empire "united" (or more accurately keeping the Sith from warring with each other).

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