So before I put some super ginormous amount of effort into forming an RP of my own, I figured generating interest first would be best, so here goes.
What I have in mind is basically a huge sandbox game, based in Hell. Any and all types of demons will be featured and basically there's almost no limit to the amount of power one can have.
Only one (or on rare occaisions, two) type(s) of power per demon. (ie. if you want to be a shape-shifter, you can't be an elementalist, vice versa)
Directly over-throwing Lucifer, or being stronger than Lucifer as a single entity is not allowed.
Apart from that, The RP will be mostly held in Lucifers courts, where I intend on having 'events' for the Hell's winter games. This includes all sorts of violent contests, basically to see which contest is the biggest and baddest and to win some favor. However, there is also always a chance for some more 'common' demons to be seen in taverns/bars/etc (demon bar brawl anyone?)
Not to mention there would also be a chance to play the part of a slave of some nobleman and cause mischief and havoc trying to free yourself from the clutches of demonkind. Or maybe you're not a human slave... maybe you're a demon criminal whose been stripped of powers and had to become a slave to pay of your debt to demon society?
With this there is a wide variety of creatures and societal heirarchies that can be played along any different story line you want.