My personal theory and hope for sunphis
I have 2 theory's for how Sunny will advance to supreme. 1 for Nephis 1st is Sunny is wrong about losing his true name and he finally takes the step himself to select Nephis as his master defying his nature. The spell told him he would become a slave after finding a person worthy to be his master. This never happened. 2nd is he fully accepts his flaw and tells Nephis the whole truth leaving nothing out of his feelings towards her. Both are great examples of his defiance of his nature.
For Neph her watching Sunny die and realizing the pain of her flaw is nothing to the loss of someone she loves. Embracing that pain to deny his death and bring him back.
And as to my hope for this upcoming fight. I want Sunny to fight Anvil and grab the Nephis's former sword that Anvil claims to have forged. This is the one Sunny modified in the 3rd nightmare.
I want him to grab it by the blade and shatter the weave and tell Anvil it's not polite to claim someone else's work as their own.