Vampires

In some "religious" magic, it's said that the magic only works if it's believed that it will work. If you don't believe it, then it has no effect. The more people who believe it, the more powerful the magic becomes. Curses, for example, I believe are possibly real. One person alone can be powerful enough to invoke a curse on someone. A group of people working together with alot of emotion involved in cursing someone can have a much more dramatic effect. What do you think? Bullshit right? Well some people were skeptics before someone cursed them and suddenly they believe. Now did bad things happen because they thought they were maybe cursed or did they just happen because shit happens to people once in awhile? You'll have to speculate.
As for vampirism, I know it exists. "Vampires" in the traditional sense is just nonsense. People who burst into flames when they are exposed to the sun, for example, is not something that is real. People who drink blood though, yes. Why do these people drink blood? Because they think they're vampires. Vampires aren't scary at all because they don't exist. However, people who THINK they are vampires are very frightening to me. So in a sense, because they BELIEVE they really are vampires, their beliefs make vampires exist. When you have a large group of people who think they are vampires and they form some sort of congregation, they become more powerful in their beliefs and thus become more frightening. You may have seen these people at some "underground" club before. Or at the mall in the "Hot Topic" type shops buying gothic style clothing or spikes or whatever. Not all of those people think they are vampires of course and are not scary. But imagine being abducted and held prisoner by someone who wanted to eat your flesh and drink your blood because they believed they had to to survive. That, I think, you would find to be a hell of a situation.