I doubt Sigyn will die. Zess seems like a person too desperate to be a good leader of anything more than a small unit. It's like he's haunted and can't keep his head cool. He would do anything for his illusory goals, but in fact it's not for the sake of reaching those goals but because he believes that as long as he's willing to do anything, he can achieve the goals. That's nothing but self-deception, of course. Even if he somehow did manage to conquer Krishna, it's plain as day Athens would collapse internally sooner or later. Extreme tyranny will never last.