What is the outcome of joining the Disciples of the Changing God
There are two ways to complete this quest.
Do the quest The Sorrow's Pray from Zaofi the sculptor. During this quest you can learn about a castoff and reveal their identity to the cult. This has no negative consequences in any form.
The other option involves the Beloved slave quest. You can learn about another castoff, but revealing their identity to the cult causes the NPC to leave the city.