[quote=@Willy Vereb]
<Snipped quote by LordZell>I am not sure involving demons and physical religions (gods are real and active) is good for the setting but exception makes the rule.
So long there won't be suddenly a paradigm shift towards people conjuring heavens and hell in an ultimate conflict I think it can still work.

Also if you are a cult supporting magic-based culture and perhaps even the old values, I guess you can find plenty supporters. And if your long term aim is to summon a powerful demon lord or something similar to dominate the world that can work, too. So long there isn't some mysterious prophecy about the chosen one or ancient sealing rituals and rather this demon lord would be an enemy which can be overcome with sheer strength if people work hard enough.


[/quote]

What about a cult spawned just from the believers of some very ancient sorcerer. Like back when magic was non-existent in some part of the country and suddenly this guy rolls in from a ship from far away and does this magical stuff. Many would start believing he's god sent. As time progresses his legends only get exaggerated and people invent new myths about him. Until: tada! You got a religion all about this one very powerful sorcerer. Now, one part of the magic would be that he consumes the life-power of people. So part of the religion is human sacrifice. In secret, he draws from this while in some sort of torpor. Getting ready to come back and rule supreme. Just a thought really, I'm not going to use this.