So some of my inspiration for my latest campaign would be the comics Hellboy & Hellblazer, and the movies Blade & Underworld. Its a story about occult detectives trying to stop demonic forces and monster-of-the-week style mysteries. I think I've got a pretty good grasp on writing the episodic, session-based stories, but really want to include some macro-based stories and conflict. No shade to 5e, but the idea of a BBEG creates too much of a super-hero-style storyline to me, so I'm trying to make something a little more, I dunno, ambiguous.
I mean obviously in my universe there is heaven and hell, God and Lucifer, but they aren't really involved in the mortal plane very much. So instead I'm trying to plan out how the princes of Hell are grappling for power to rule over humans as shadowy organizations. So not really "cults" per say, because these gangs are made up of demons/monsters, but also not really organized crime. More like the vampires vs lycans of Underworld, but I want to make it more Game of Thrones like with multiple secret factions that are all stabbing each other in the back after forming fake alliances. However, the PCs are then trying to take down these secret demonic groups as these groups are fighting with each other to rule the world.
So I'm struggling to find some good tools to plan out these macro-level conflicts and stories. A lot of what's out there are for open political factions that are made up of say the monarchy, banking guilds, etc. Which doesn't quite work since I want my groups to be hidden to all the humans. Or there are tools for making cults, which also doesn't quite work since I want my groups to not be religions with disciples but instead back-stabbing gang members. Or there are tools for making thieves guilds, which also don't quite work since I don't really want my PCs to gain renown with these guilds, but instead eliminate the guilds after discovering them.
TLDR: Can you point me to any tools for making rival demon gangs that work in the shadows to take over the world?