Quote Originally Posted by endoperez View Post
There already exists a game in which boogie monster is real, the kids are scared and need to be protected by belief-based magic. This one stars the kids, but I assume it'd be easier to tweak change the protagonists than the whole system.

I don't know how good it actually is.

http://www.littlefears.com/
I've read both Little Fears editions. In my opinion, the first is pretty mediocre, and the second is solid. They have a very different concept, though.