[@El Noche] The demons are suppose to be like the demons from the anime Maoyū Maō Yūsha. They would look mostly human but would have traits like horns, tails, or even wings that would distinguish them from humans. High level demons like the prince and soldier can hide their demon traits using magic. Also The idea is suppose to be that the demons and humans are actually very similar and they have forgotten the reason as to why they are even fighting.