Well maybe not, but for me it was an essential part of my book. I wanted adventure and excitement, and for that your main character needs to experience danger. So I invented a bad guy and a monster.
In a book, especially a fantasy book, you are free to conjure monsters in whatever form you wish them. Their desire to kill, maim or feed needs no explanation, it is what they are. Think of the Alien in the film of that name, we don’t really need to spend too much time thinking “What’s made her so angry?”
There is something very frightening about an inexplicable relentless killer and the fact that the victim doesn’t know why they are being pursued just adds to the suspense. And in a lot of cases a human can be portrayed in the same way. In real life the monsters are other people. Psychopathic serial killers may act like something out of your worst nightmare, but they are still human, at least physically.
Personally though, I think a true bad guy is better for some motivation, a back story or a certain charm, even a few redeeming features. I recently read ‘Cross Country’ by James Patterson. I don’t read a lot of thrillers, but I enjoyed it. Fast paced, lots of action and short chapters with a good twist at the end made it a good read. However if I had one criticism it would be that the main bad guy was one dimensional, a great nasty character but just not enough back story to make him interesting.
Maybe it’s because I’ve studied psychology that I like to know something about the motivation of such a character. “What made him the way he is?” is a question I want answered. I’m also fascinated by the apparently normal components of an evil character and how they can throw the psychotic into sharp relief. Hannibal Lector’s most famous line from ‘The Silence of the Lambs’ is probably
“I ate his liver with some fava beans and a nice chianti”
“I ate his liver” is a pretty chilling line but it’s the addition of the fava beans and the Chianti that makes it so iconic.