In principle, any religious organization, monastic order, etc., not necessarily of a good alignment, would be a fresh idea compared to what's already been done.
1) Artery and its heresy (but heresy isn't a very good group)
2) Heckelian dynasties and their pantheon
3) LEGENDS, which, in my opinion, are too vague for such a concept
4) Demon worshipers
Considering the specificity of the last two options, only what I described earlier remains.