Here are my reasons.
1. To combat a sanitised view of Christianity
More than once, I have come across the idea that once you become a Christian, your major sin habits are largely solved. People have a wrong-headed notion that a new convert will instantly give up their habits of clubbing, swearing, working on Sunday, and so on. This is simply not true. The Christian life is a constant battle with sin, and things can still get ugly. Additionally, true Christians still struggle with horrible indwelling sin. My portrayal of Nazt in these books (while difficult to handle) was a deliberate attempt to show the reader how all sin is ugly and how controlling and sly it can be in an attempt to rule our lives. The imperfect characters who battle for good and just causes also demonstrate this. Yet in trying to depict these things, I wanted never to let go of the truth that we always have hope and that whenever we turn to God and call on Him in repentance, He will answer.