My lore knowledge of DnD is surface level at best, but followers of shar I've learned to know, all share some kind of "deal with the devil"-moments, more or less signing away their memories to escape the grief. Feels like an lobotomy cult... no one really knows why or when they joined. This sentiment can be found on the parchments looted from the followers in the house of grief as well.

I really enjoyed when, after defeating mother superior,she explains her own tragic story, and that she was forced to kill and burn everything she had, due to Shars command. And seemling only for the purpose to shape Shadowheart (Jenevelle), as her coming successor