There is the Darkside Verse by Sakuri, but that is really Dean/Cas. Here be demonic Winchesters, fallen angels, evil Team Free Will, language, violence and slash.
If you might be interested, the masterpost is here:http://sakuri69.livejournal.com/4520.html

There is also the author Highermagic. She writes lots of demon verse. She has tags for creature: demon!castiel, creature: demon!dean,
creature: demon!sam. If you are interested in checking out her journal, here is the link: http://highermagic.livejournal.com/

Thank you very much for the links~!

A self-rec you may enjoy :
My Brother's Keeper (http://monicawoe.livejournal.com/37911.html)
This features a future where Sam and Dean are feared by Heaven and Hell.

I absolutely love this! This was amazing!!

I have another self-rec for you. Features demon!Dean & Wincest.

A Love Unholy (http://mznaughty01.livejournal.com/1083.html)

Edited 2012-06-25 12:05 pm (UTC)

Hey, if you're still looking, I have one.


http://www.fanfiction.net/s/9212130/1/Demon-of-Death

(:

Bound Together
http://emeralds75.livejournal.com/3985.html