Posession (Not By The Devil Or Demons)

My main character gets possessed by the soul of a girl who got reincarnated inside of her body. The soul happens to be that of a really *slutty*, fairly insane teenage girl, and when the girl takes over my main character, she causes my main character to sleep with people and get high and act out and all kinds of things like that, that she would have never done. The part I'm at has my main character being kidnapped by the gods, and when she is with the god of peace, she wills the soul to take over, because she herself doesn't want to get high with him (Yeah, the god is a hippie-like dude) and so the soul does, and then she causes the main character to give the guy *fellatio* (fancy word for oral sex x.x) and the main character is kind of just watching her body, from inside her body. She doesn't actually feel much, but she feels a little bit. It's drastically lessened. And my main character can hear, but it sounded muffled when the soul was in control. I want to develop the soul taking over her body thing so that eventually, the soul is reluctant to give my main character control of it, because the soul likes having a body of her own again. I would like to make my main character fight the soul for control of her body, but honestly, I have no clue how to write it. If you guys have ANY ideas on this, please comment on this forum. I NEED YOU!

You can write them as observers / peanut gallery / Greek Chorus to each other. Whoever is in control, the other is the Chorus. As far as the fight for control goes, you could have one take over when the other falls asleep, and so, they would try to stay awake which would make them both a bit crazy and paranoid from sleep deprivation.

Look into DID (Dissociative Identity Disorder) and "healthy multiplicity". Those can give you two sides of the same coin and some places to start with as far as how to write this, as well as how people live with something similar to what your characters go through.