I like characters with depth. When writing thrillers/horrors/psychological types of books, I want my characters to have a depth to them. Because in many ways, whether it be the killer or the victim, the character needs to have many levels to them. Because they go through situations and traumas, they need to have a certain understanding or lack thereof. It makes the character someone worth reading. Take my techno killer, and there is so much there to this character. This killer leaves much to the unknown. Why for me, if I were reading about him, I would want to know why. Why? Why do characters feel the need to do what they do? What kind of past did they have, or are they just pure psychopaths? The development of a character is important to any story. Without the characters, there is no story. This is why I like to put all I can into developing their mental status and who they are as a character. And in many ways, once I have the character, the story kind of develops from the character.