Your saying "the very that DESTROYED the Cetra is convincing Sephiroth that HE IS a Cetra."
Who are you talking about ?

Actualy doing more research your right on 1 thing it s what he isnt an ancient and he know it. But all the rest is all correct here is more.

Sephiroth know what he is. He doesnt need convincing.


Aeris: Sephiroth is different. He's not an Ancient.

Cloud: He shouldn't be able to find the Promised Land.

Sephiroth: ...Ah, but I have. I'm far superior to the Ancients. I
became a traveler of the Lifestream and gained the knowledge and wisdom of the Ancients. And soon, I will create the future.

Aeris: I won't let you do it! The future is not only yours!

Sephiroth: Ha, ha, ha... I wonder? Wake up!

Cloud: Shut up!

Cloud's controlled soul appeared.

Sephiroth: There, Cloud... good boy.

Cloud: The... Noise... Wa...... aaaa...... aa...

Cloud's controlled by Sephiroth and gave the Black Materia to him.

Sephiroth: ......Well done.

Sephiroth disappeared. Later.