The narrative reason is to infiltrate the cult and learn more about the tadpoles
once it becomes clear that none of the local healers can offer a cure.
Soft disagree.
The tieflings are literal refugees with nothing to offer. The only reason to help them is out of the goodness of your heart. Once you talk to Halsin, siding with the cult provides a better chance of survival until you learn more about the tadpoles.
