I try to avoid them if I can. I see them sometimes herding their flocks of flabby grey creatures into and out of Boston harbor, and it always gives me the chills. Briano tells me that they brought me back to life, but I can't remember it. I can't remember a lot of stuff. He also tells me that I was good friends with one of them once. One of the ones that begs outside of Grand Island Bank for nickels or blood. I can't tell you why I'm uncomfortable around them. They're just fish.
All spell casters gain their abilities through a form of demon possession. So in order to gain magical abilites, PCs must track down and trap demons. Of course there are some pretty powerful demons, if the demon is stronger than the PC, the PC could find themselves subjugated to the Demon's will.