I'm suddenly realizing something else about the story. It doesn't have a main villain, not really. And it makes sense in hindsight. Way back when they first revealed Kethric, they said he was a lieutenant of the main villain, like the other three chosen. And I think that's how they're written
Look at it this way; at the start of the game in act 1, our main enemy is the vague concept of the Absolute and its cult. But then Kethric becomes the main villain for act 2, but the Absolute is still above him. And then the reveal. The absolute is actually a lie, a tool, wielded by the chosen of the dead three to enact their masters plan. But... the dead three never take centre stage, and set 3 has the looming threat of the elder brain, which is the absolute, breaking free, something even the chosen are worried about, so we have to worry about that. And we kill yhe chosen before the end of the game and the final battle is against tbe brain, which is never an active presence in the story. So... who is the main, central antagonist?
Yo don't HAVE to kill all of the chosen.
I honoured my deal with Gortash and we went to face the netherbrain together after I killed Orin and got her stone. Him holding on to his stone, and me carrying those of Ketheric and Orin. We can't control the crown however and the brain blasts Gortash before the emperor appears to give us shelter on the astral plane. So in this path, Gortash is not a villain with respect to the player. We're both villains. I haven't playeed the inverse , kill Gortash and keep the pact with Orin, but somehow I think Orin will want to kill you anyway.