I think it's due to having a fascination with the unknown in general. The dark seems mysterious, and it draws you in. While I'm not into creepy things per se, I like exploring the dark side of human nature through classic literature, crime shows, music, etc. I've been drawn to cynical writing in general. I don't relate to evil characters, but studying them has an appeal to me, like what is going on in their mind, what drives them to commit the acts they do. I speculate on why, and see what the evidence says in the storyline. It seems that darker characters in literature are written in a three-dimensional way, you see many aspects of their personality. Whereas the heroes in literature, you have a glimpse of how they are, but you don't really get the full picture that often. Another aspect is that I yearn for poetic justice against these types of people for what they do to others. Understanding their motives is a way to urge others not to go down that path. It's also a mode to protect myself as well, knowing about the darkness to avoid it. So there's an element of self-protectiveness as well as understanding people.