Since we have taken so much from Dresden's style magic already, we might as well take a bit more regarding demon summoning.

It takes only a small amount of magical energy, but if you summon something outwith your control, it will most certainly kill you. To summon a magical creature(be it a demon, spirit or other being of the Fae) you must know it's True Name. Speaking it three times is required to fully summon it. Calling demons is easy and relatively straightforward, and it doesn't always need to be for combat. Summoning a demon inside a circle and bargaining with it can net you a good deal, depending on the demon, and there are people who are willing to summon them for you to bargain with, for a price. Calling a demon, binding it, and forcing it to fight will annoy the thing to no end, and it will try to kill you if it gets the chance. Naturally, attempting to call a much more powerful being (like the Dread Wolf, Fen'Harel) probably won't work. Even if it does, you might hope it did fail =P

I'm working on a post as we speak, but will hold off in posting until Apollo and Leos have had a chance ^.^