I have an idea about a demon arriving in our world and possessing a mortal. As any other proper Succubus\Incubus that one will feed on sexual energy but it will start with a meager amount of power: imprint a single thought, make dick hard, make minor illusion and other stuff like that. Also, I consider doing that similar to this story: https://chyoa.com/story/adventure/cover RPG with people using comments to control a demon in his\her quest for mightiness. Probably I'll make a much simpler system, with only few attributes, the one used in Adventure is too complex and cumbersome Will be there any interest for that?
There already is a story that has something of that theme: "A shadow succubus" has an incorporeal succubus that possesses and switches bodies with her victims, both male and female. On the other hand the story does start with her being able to completely posses the victim but so far hasn't had her modify the bodies at least yet. Personally I like that one and your idea sounds good as well.
