I don't know if this helps you or not, but I was born with and raised in a fairly interesting Christian church... many call it a cult. They make a big deal about actually reading and following the Bible... when someone gives a talk at the front, everyone follows along in their own Bible. Their largest beliefs were everyone is born in sin and in order to be 'saved', you must repent, be baptised under FULL immersion, and speak in tongues. This is according to Acts 2. Everyone there was baptised and could speak in tongues. There were many testimonials every week about faith healing (everything from colds to cancer) and occasionally miracle interpretations of speaking in tongues. There were 3 meetings a week (must be attended), plus a youth group meeting as well as the occasional Friday meeting and a prayer and fast every six weeks. Two week camps in various parts of the world, you could pick which one/s you wanted to go to, was a very interesting experience. They slammed other religions, especially other Christians and most of all, Catholics. Claimed they were the one true church (they never called themselves a religion, just simply 'the truth'). We were taught that our real friends were within the church. There were many, many... many rules. They were called 'guidelines' but if you disobeyed them you would be suspended from the church for a certain period of time. If you were suspended, all members of the church, including family and friends were forbidden to talk to you (or they would have the same consequences). Even more so if you decided to leave... you would be shut off from your family. Rules included no smoking, no drinking, no swearing, no night clubbing, no fornication, no dating anyone outside the church (plus dating rules like the '2 second kissing rule'), no homosexuality, no communication with people who have left the church, no following careers that involved being potentially famous such as singing and acting, no gatherings of more than 6 people, no talking to the opposite sex for more than 2 minutes if you were under 30, no living together unless you are married, no reading self help books. I got talked to for 'liking my pet parrot too much'. Women with careers and wearing pants was frowned upon... men and women had their own distinct roles. Think 50s. Child care centres and people not smacking their children was considered disgusting. Seeing a doctor was frowned upon and seen as not having faith in God. I was suspended a year ago (I can PM you the reason why... I have no problem talking about it but it's a bit extreme to just post here) and have changed much of my thinking since then. No, I don't plan to go back. I don't know where my faith stands at this point, I think I'm more agnostic than anything. Many people have satisfaction going there and it is their entire life. However the moment your life and opinions conflict with the rules, it can destroy you. I hope this helps you in some way!
I think I have your answer. Do some research regarding the historical crusades. This might help you gain some interesting view points regarding peoples religions and the lengths they will go to prove they are right. As many of the more advanced responders stated, "this is a loaded question." Maybe try to narrow down your selection and fine tune the detail in character and plot. Try thinking of friends you have who are religious and hang out with them. Talk to them about stories, upbringing and way of life. Sitting down with someone and hearing it first hand is a great tool in story telling. Wish you well.
