They never really expanded on it since ARR, the latest being the Amdapor Keep (Hard) dungeons. The only lore we have says it's a doomday cult that started when the lesser moon started its descend. It's not even clear if they moved to worship Bahamut or not once it been revealed it was its prison. I don't think there's any mention of them being tempered either. Some would argue they were exterminated once they freed Ferdiad, but don't quote me on that: we absolutely don't know what happened to them next.

Personally I feel it would have been nice to have a bit more minor evil organizations like that. It's been so long we've seen them, I doubt we will ever heard of them again tbh