So here's the idea...
Everyone (well, at least most people) have some sort of conscience. There have been many theories about the human "soul", everything from complicated religious structures to children's cartoons featuring angels and devils arguing over a character's shoulder. Turns out, the cartoons weren't too far off. At the moment a human being is conceived, 2 other being come into the world- one "good" and one "evil". These invisible, powerful creatures feel no emotion other than an insatiable drive to complete their missions, which they have known since their creation. These they cannot and do not question. The Iustus, the "good" being, is tasked with keeping the child on a moral path. Its concerns are with selflessness, honesty, duty, and a sense of justice. The Scelus, or "evil" being, is determined to keep the child on a path of selfish ambition. Thus it values self-preservation, pleasure, ambition, and vengeance.
The strength of each of these beings determines a human being's outlook on life, and the way they view the concepts of good and evil. Most of the time, their powers are relatively balanced- hence the general concepts of morality agreed upon by most of the world: things like "fairness" and "revenge". Yet every so often one is created much stronger than the other. These result in the great heroes or villains of the world. Most ancient philosophers had either a strong Iustus (think Plato and his concept of "the good") or Scelus (think Hedonism). Same goes for religious leaders and icons, or leaders of political movements. Anybody with a set of ideals so strong it could change the world. As for those without a conscience, their beings were never created for some reason.
At least, that's how it's supposed to work. Enter Jason - a boy with no conscience. It's uncommon yes, but not unheard of. Except he wasn't conceived that way. Jason had and Iustus and a Scelus, both at the exact safe level of power. Perhaps this is why things went wrong. Whatever the reason, both creatures were separated from their host, manifesting in physical forms. Both trapped in the human world, they have begun to develop emotions. Constantly at odds because of their opposite personalities, both are determined to be figure out what happened and get back to guiding Jason, preferably without the other one there. But human emotions are... complicated. And the two beings may soon begin to realize that the world isn't as black and white as they'd like it to be.
Well, that's my idea ^_^ I'll work on fleshing it out a little more once I see if anyone is interested. I'd be willing to play either character, and they can be either gender. 18+ is not required, but if you aren't that old, please let me know so I know what topics I can safely get into. (Nothing too vulgar regardless, that's not really my style.)