OPEN
This roleplay would be set in the distant future, a good few centuries to a millennia. Working human technology exists only in the human shelters hidden throughout the world. Any human technology outside of human bases is FUBAR, and is found primarily in ruins.
Demons have two forms; their true form, and their human shells. In their true forms their demonic powers are almost limitless, but they run the risk of fading back into Hell if they stay in their true forms for too long. For this reason, they either have to steal human bodies, or craft their own flesh (usually reserved for the more powerful and skilled demons). I know I mentioned Hell before, but we don't have to go biblical with it. In fact, I'd prefer it if we didn't. That being said, in the roleplay, there is a "God" and a "Devil", so to speak. This isn't central to the roleplay, though. The main focus will be on our characters.
Demons took the world by force, and obliterated the majority of humanity. The few humans that remain live under ground, or have been captured by demons. So many centuries have passed that no one knows for sure what year it is anymore. All the human cities have been destroyed, and replaced with magnificent, ominous demon cities. Even the flora and fauna have started to change.
A large, human base located in the mountains is attacked by demons. Hundreds were captured to be slaughtered as livestock, or sold as slaves. A few dozen were killed in all the mayhem. A small handful managed to escape. Over the weeks, the group got even smaller, most dying of starvation, a couple being picked off by demons. One even left, screaming that she would be better off without them.
Eventually, she came across a demon city. Starving, lost, and sleep-deprived, she wondered in, searching for somewhere to eat and rest. She eventually finds an inn, where she meets a demon who she tricks into believing she's a demon. Initially, her plan is just use him to get to a blacksmith, but after he listens to lie upon convincing lie, the demon insists they travel together, as they're headed in the same direction.
It's only a matter of time until he figures out what she really is.