I'm agreeing with septembers_coda here. I really liked it (admittedly, I have a soft spot for fics that explore different mental twists). It didn't feel like horror at all. Well, at least if you think of it as that Sam will eventually find his footing and that if part of his mind created Dean for X years, then some part of that 'personality' will live on. The clash in personalities would be like a train wrack though. ^^