I'd like an open world RPG where you play as a demon trying to survive and eventually thrive in the human world by killing other creatures and devouring their life essence. You'd start out as a lowly imp feeding on farm animals and the occasional homeless man and work your way up to a powerful demon lord. As you fed you'd gain experience that you could use to alter your form or gain new demonic powers; wings, sharper teeth, being able to shoot fire from your hands, a shape shifting ability to better blend in with human society. As your power grew so would your hunger and you'd need to move on to more populated and dangerous areas. The game world would consist of at least one large city, several smaller towns, a few isolated farms, a forest, and a sprawling countryside, all inhabited by both humans and other supernatural creatures, some friendly, some not. Aristocratic vampires in the city, mermen in the bay, a slenderman in the forest, rogue werewolves, a chupacabra, ghosts in abandoned houses, crocodile creatures in the sewers, and a clan of demon hunters trying to bring them all down. If you're caught killing someone, and especially if you're caught using supernatural powers, awareness of you will rise, and police, military, and demon hunter presence will increase in the areas you were seen, eventually forcing you to either move on to new hunting grounds, severely weaken your opponents, or kill some other troublesome demon and frame the crimes on them. You could either be stealthy and disguise all your feedings as ordinary murders or accidents, or you could declare war against humanity and destroy all in your path. How you carry yourself will affect how the other factions view you and whether they'll help or hinder you (the heavily entrenched in society vampires won't appreciate you raising suspicion of supernatural activity in their city, but the werewolves might respect someone who brazenly flaunts their brutality). Your eventual goal would be to drive the demon hunter presence out of the area and declare yourself the ruler and most powerful supernatural being of your domain.