This is a quirky little question that had the chance to possibly turn me inside out…
Day 21: Favourite RPG Setting
Lords of Gossamer and Shadow is a cheat answer. There is a core setting to this game being a central staircase that winds its way through all realities and you play the role of practically a god, but in reality it is an open setting. Your character goes into other worlds and interacts there in these Gossamer Worlds that are all separated by Shadow. So while it is not strictly a universal game concept it can play like one so if I offered it up as an answer I would feel like I was cheating somehow. I always feel like people that offer up FATE is cheating so I will not do the same although strictly that would be my choice.
Instead I will go for the critically acclaimed FATE based game The Demolished Ones. You awaken with amnesia in a strange yet familiar city. What is going on? Who are you and who are these people around you? Play the game and find out. I will not say really anything other than the setting is similar to a Victorian London and will become the rabbit hole that you fall down. It is a brilliant game and if you do not have it, then get it. It is penned by the brilliant Brian Engard and published by Rite Publishing. Keep rolling!