I'd like to know everyone's thoughts on how to run a PC posessed by a Demon - not just sponsored by one, but actually sharing the bod of the PC. If anyone's read the Malus Darkblade books, this is the kind of setup I'm going for.
I was thinking Sponsored Magic (Hellfire) would be logical, and some kind of debt/stress system to temporarily buy powers such as Inhuman/Supernatural Strength/Speed/Toughness/Recovery, Claws ect. with the caveat that, if the powers exceed the PC's refresh limit or some other limit (this is where the idea of a 'demon' stress track comes from), the Demon takes over, and the more the PC draws on the Demon's power, the more likely it is to try to take control.
The Demon taking control would take the form of a temporary blackout, with the PC waking up to find themselves in a bad situation (for example, running along the edge of a canal in the middle of a thunderstorm three hours later with armed cops in pursuit) and having to find out what the Demon did.
Thoughts?