I was thinking of running a homebrew setting for a game coming up one in a setting very similar to the Dresden verse but with one major difference magic is evil. To use magic you need to draw on chaos to help get past the natural order of the Universe and the more chaos you draw on the more you are warp until you become a monster. So the premise is that all the supernaturals vampires, werewolves, demons etc where once wizards who drew to hard on the forces of the universe. The PC will be playing either hunters tasked with destroying such abominations or as S013 the Special Magic Unit of the London Metropolitan Police, I am not sure yet.
Now the question is how do you make magic feel threatening and dangerous without making it impossible to use. I was thinking of letting wizards cast of a seperate corruption stress track and consequence tree and any consequences they deal themselves being permanent. So you can safely cast 4 times a day a scene but any more and you are going to destroy yourself pretty quickly. Does anyone have any ideas?