It's only an idea as of yet but I think with some collaboration from the RPG community it could be something really good, here we go.
It's said that underground there is a sprawling metropolis of sin and vice but also of passion and beauty, it's called Darkton. It wears rags and finery, it dawns cloaks and feathers; it is heavy and dark but also a bright fantasia of color and life. In Darkton, good and bad don't exist, they are grey spots where nothing can be discerned from the other but instead of grey, it is multicolored and flamboyant, kind of like it's people. You may be new to Darkton, you may have lived there all your life but once you are there you can't leave, not because something is holding you back, but because you are holding yourself back.
However there is evil a foot in Darkton, something is not right, it is a faint buzz in the air, a dead body in a ditch, a string of magic related crimes, there is evil a foot in Darkton, will you find it?
It's only a skeleton, I have a flimsy plot but I need characters to bolster it, I need you guys to help me make this pile of writing something RPable.