I think everything turns on when this is taking place. If it is current, then the war is a big issue. If its back at Storm Front, there is more wiggle room.

As far as villains go, the dresdenverse has so many groups, both good and evil, that I have lost count. But if it is the ThreeEyes we are talking about, the White Council, depending on the war, might not have the man power to deal with a single drug cartel.

The Blackened Denarius would be interested because if they dump a massive load in the city's water supply, well that is enough panic for them to feed off of.

We already mentioned that the draw for the Fae would be significant. Lets face it, what easier prey is there then someone who has no idea what is going on and the first thing you see is someone like Maeve.

I doubt the vampires want anything to do with it. I'm not sure how giving the sight to normal humans will help them with any of their agendas. But lets face it, Mavra is crazy.

The two others that might have stock in this are the Outsiders because yea, and the Dragons because they are the single most under used faction in the Dresden Files.

Having said all that, come on, there is no real good guy in the series, save for the Knights of the Cross. The White Council oversees all magic in the world but even they can't make a "good" decision without twisting it inside out.

The Drug though, that is an iffy thing. The drug does wear off, and it was the product of Nemesis playing with Victor Sells. So if the Council gets involved, chances are if a character takes it again after they have been warned not to, they are dead walking. So here is what I think, rather then having them take it again, just say that they have taken it a few times before anyone catches wind, but now these few are showing many of the characteristics of a Ley Line, turning them into founts of energy that anyone can tap into.

Lastly, I can see my self playing a junior member of The Wardens, or if the Blackened Denarius are involved I can play a member of the church.