Magic Forums

I've been thinking quite a bit about magic and casting these last few days. When I cast, I call to the elements or to nature. But I'm curious about the other sources that people call to? Some are misled by tv and movies and believe we call on many other things: the devil, god, a power from inside, nature, the spirits, certain deities, demons, a huge source of energy that only some can receive, the moon, etc. And some of these are true. What do you call on when casting? What provides you with the most power? Thanks!