Doesn't sound too realistic. Those murderous sects ought to be full of... well, murderers. Psychos and other people of zero sympathy for anything. It doesn't seem like a bunch you could unify behind any cause. They can work as relatively small forces centered around strict and ruthless leadership. However, if it starts to grow, wouldn't infighting be inevitable? They are all cut-throats, after all. With no honour present, they would spare no effort to use poison and other underhanded methods to remove competitors. Or Mara.