I wrote one that is kind of what you're looking for. It deals with Dean's return from Hell, it talks about the deal and his purpose and it has lots of Hell flashbacks/dreams. It picks up after the end of episode 4.03 and goes all the way to the apocalypse. Finished at 14 (long) chapters long, general, with warnings for language, themes and gore. It's called '66 Seals of doom on the wall' (link: http://adrenalineshots.livejournal.com/9000.html)