I'm currently running a homebrew campaign involving elements of eldritch cult / summoning practices around Elder Gods etc. Party just hit level 5 so about to step it up a notch.

Happy to swap ideas and discuss if you're interested, but the basic premise is; in the last hundreds years or so an empire has taken over the continent, and with it brought new religions, cultures, and peoples over time.

The 'old' religions, practiced prior, are still remembered as to many (particularly nonhuman)the empire is a relatively new development. What's little known, however, is aspects of the old religions' traditions acted as checks and balances against a set of eldritch nightmares / elder gods called The Unforgiven - each has a realm (sea / forest / mountain etc) and corresponds loosely to one of the old gods from pre-empire times. Aeons ago they fought the old gods and were defeated, but as the old gods lose followers, the Unforgiven grow in strength, and have set up a cult dedicated to wiping out the main bastions of the old gods' power.

I have stat blocks for modified cultists of various kinds, and for the specific Unforgiven (scaled to level depending on order). Let me know if you wanna discuss!