Yeah, I tend to forget them too. It's odd that I would remember them, to be honest. But yes, I think a rogue demon would be good. Maybe one disguises himself? I can make a CS for him so we both have a share understanding of what he looks like and is like. 

As for modern or medieval, I think I've got it. We could do an alternate reality to the real world where everyone is magical in someway. Like, Humans would use magic and those of them that are not just commoner's or slaves would be scholarly magicians. They would have everything that we have but, it would be more.. magical. So, music would be like, the Three Witches, Mara, Clara, and Casey singing My Unicorn Ran Away. That sort of stuff. Phones would be around but would be magically inclined, as in, only available through Magic. So if you are say, a slave, and your magic is stunted, you would not be able to have a 'phone'. So let's just say the phones are both physical objects but only operable by magical means. Same with cars, you would need magic to run them. They would also use winged horses and other such magical creatures to get around. And factories would be run by magic as well. 

I'll start working on a CS for our villainous villain. :D