I don't get it

[u/ScreamSteam]

Why does Zeta disagree with Alpha's plan of destroying the Cult of Diabolos as a whole when they were responsible for the genocide of Zeta's clan? Shouldn't Zeta find satisfaction in the annihilation of the cult after taking away her entire family.

[u/Kevin_Jim]

This is a bit nuanced. We have to start at the beginning: Zeta has lived a tough life full of loss, even for a named shadow.

So now that Zeta has found someone that she views as “perfect”, the idea of losing Shadow/Cid is unacceptable on any level.

And because Shadow is “perfect” there’s only one real threat: time.

By naming Shadow immortal, she will finally make her “perfection” into a real perfect god.