It's a bit early yet, but I've been brainstorming ideas for what I'd throw at a group of PCs, assuming I can get a game going once the rpg is out. Fortunately, some of the ideas I've had seem to gel fairly well with what Iago has posted regarding the Laws of Magic.
Anyway, I'm going to post the rough notes I have for some bad guys. If you have any villains in mind for your own game, I'd like to hear about them.
As a general rule, I'm going to try to distance my characters from both the White Council and the metaplot of the novels. The reason for this is that most of my potential players haven't read any of the books (but I'm working on that). I'm going to focus on threats that the WC doesn't have the time, resources or inclination to investigate themselves.
1) Werewolves.
I like the Dresdenverse werewolves, especially the Alphas. I figure that since the Alphas are mostly college kids, they'll have friends and family that are based in places other than Chicago. I think werewolfery is then going to spread beyond Chicago, as they initiate others and those others start their own packs in other cities.
Now the Alphas generally just patrol for supernatural threats, but their progeny might not be so discriminating. I'm thinking there are going to be some mundane muggings and serial rapes that are going to be stopped by the local 'wolves. That's all well and good, but there will be violations of the First Law by these well meaning kids, and that's going to lead them down dark paths. Enter the PCs.
2) Half-vampire Mobster.
So there's this mob boss. He's a man of will and determination. Nothing happens in his territory without his say so. The Reds try to take him. Now, he likes the strength and other advantages of the half-turned vampire, but giving in to the Hunger and completing the change doesn't fit in with his other goals. He's a sociopath, but one with free will. He's the master of his own destiny.
3) Assassin Wizard.
He kills people for money. Black magic, right? Not quite. He uses completely mundane tools to get the kill. Guns, knives, piano wire, whatever. He just uses magic to get away with murder. Veils to make sure there are no witnesses. Tracking spells to find his prey. Maybe he gets the Lawbreaker stunts, but they don't hit as hard as they would if he just made his targets bones explode.
4) Wizard cult leader.
I can't remember how the Law is worded, but it's the one that says "No Jedi mind trickery". Well you don't need magic for mind control. Cults have mind control techniques that also work. This guys uses those instead of magic. His modest magical talent is just used to lure new recruits. And his church allows multiple marriages (for him, anyway), so he has dozens of wives who have given him scores of children that have been brainwashed since birth, along with being trained in the art of magic.