I have had this idea for sort of a middle ages setting with magic in it. But magic is outlawed. Think about inquisitions and that sort of things.
Humans have weary little magic and those who have it are hunted by the inquisition, there are other things in the world. Humans are the only and primal race but there are all sorts of monsters in the deep black swamps and forests. So basically anything is open.
My character would be a young human girl who gets taken by the inquisition in a small border town, bordering on the unknown dark forests, swamplands and spooky mountains that are forbidden. She is accused of being a witch and imprisoned after the inquisitors come for her and have a bit of a talk with her first. She is placed in a carriage and they want to take her back to the principle city. There is an accident on the way the carriage crashes and the inquisitors are knocked unconscious, she can free her self but the only place she can run are the forbidden forests.
A place ware no humans live and nobody has ever come back from.
The game should be a dark mood with all sorts of vile evil things happening to her, I would be looking for a writing partner who dos not mind BDSM and light torture scenes. This is basically the story of what happens to her at the hands of all the evil and dark creatures of the forests. [Take your pick from devils/demons, evil fey or whatever you feel like]
The game can be free form or d20 system it is all the same to me