@lin This is a really good question. **incoming ramble, please assume crash positions**
When I first began writing fantasy, I adamantly believed that incorporating a “God” character in my story was a Bad Idea In All Caps. The reasoning behind this is that I, as a finite human, could never portray God in all His complexity. This thought was only reinforced when I read this book, set in modern times but with a very obvious spiritual battle going on. And “God” was… passive? Favoring the authors favorites with about as much subtlety as the author? Distant? It made me think “ew, if this is what happens when someone tries to write God, leave me out of it.” But I’ve changed my mind in recent years, if only a little bit. You see, while it would be near impossible for me to figure out what God would do and not do on my own, writing anything on my own is Not Good anyway. If God wants me to write Him, He will help me.
But, here comes the grey area I think we’re all talking about here. When writing his-fic/contemporary fic, those are already places where we know God to be. Even in the Chronicles of Narnia, Narnia is connected to our world, so if God exists here, logically, He exists there. The choice whether or not to overtly include Him is between the author and God.
So is writing a God character into a story in a different world idolatry? After all that, I still don’t know. I’ll just explain how I deal with this in my own writing. There is an absolute standard of good and evil. This standard exists in my fantasy world. So things that are true here (i.e. forgiveness is a good thing, hate is destructive, even in the darkest times there is still hope.) are true there. So, even without overtly including God, I can include His truth. But can there be truth without a Truth-giver? Again, I don’t know. I’m no expert, this is just my own reasoning. I’m still learning, or course. 🙂
*shameless self promotion* https://weridasusual.home.blog/