Where the Sidewalk Ends by
bellatempleGen, PG-13
Dean gets out of Purgatory and he can see the gaps in the real world where the pieces don't fit together.Things are peeking through the gap--eyestalks and squirmy tentacles and bits of fingers, long scaled bodies slithering by, etc. And it's hard to explain how 'the walls don't fit the ceiling, Sam.' So he doesn't say anything and goes about his business. But he knows he's seeing Purgatory, and worries that eventually something's going to reach through a gap and drag him back.
Untitled by
ceedeeandco Gen, PG
The plants and trees are monsters, too.
Matter of Time by
mysticallight6Gen, PG-13
Speaking of demonic Dean, let's say that while he was in Hell Dean started the process of transforming into a demon. Cas halted that process/cleansed that side of him when he pulled Dean out. But all Cas could do was cover it up - part of Dean's soul was still permanently something other than human. Enter Purgatory, a place built to hold monstrous souls. Dean goes native to survive and sort of reverts back to how he acted in Hell, right up to the back eyes (or white eyes :3).
Cas can be present or not. If he is, I'd like him to not be as bothered by this as a human would be. I love the idea of the angels having their own alien morality - plus, he's crazy.
Maybe Sam rescues him at some point and they have to deal with this new (old?) side of Dean.