Fantasy authors create religious systems that add to the immersive experience of the fantasy work by drawing from real-world religions and mythology, embedding religion into everyday life, connecting religion to politics and power, allowing diversity of beliefs, and making the religion affect the plot and characters within the fantasy narrative.  

Contrary to popular belief, fiction writers do not just make everything up. Writing compelling stories requires research! Research sharpens accuracy, helps craft believable worlds, and creates authentic characters and stronger plots.