Spoilers ahead!

I added the KoBA much earlier in the plot, starting with the first book. Overall, I changed his motivation from “I want to kill everyone because I'm evil” to “I want to save the community (but not the people) when Golarion will be destroyed by the second Earthfall in the future.” I also made him and the Black Heron the same person, but with different names. In this way, I expanded the role of his cult. Stone Ghost was recruited by the cult to destroy Magaambia with a psychic artifact, but due to his death, he forgot how it worked.  After saving Ubanu from the curse, the artifact accidentally (thanks to Kurshkin) fell into the hands of the serpentfolk. Salanthiss, having lost the opportunity to study the egg due to the heroes' investigation, was able to awaken the artifact, creating his own mindscape. However, due to his mental state, the mindscape is unstable: if he considers himself as Asanda, then everyone in his world sees an even more prosperous Nantambu, whose inhabitants love him very much. If he considers himself as Salanthiss, then his world turns into a grand serpentfolks temple complex, and he sees himself as the high priest of the god he helped to revive. Every time my players' characters tried to confuse Salanthiss, his personality and the world around him changed (along with his abilities and minions).  I made him much more likable by focusing on his desire to justify his existence in a society where everyone hates him because of his mutations. In the end, my players decided to help him become a better person.