If This Be Madness by
sweetmelodykiss 2100 words, warnings: "Dark fic, bottom Snape, non-con, breath play, bondage, torture, but not too graphic, kind of a happy ending." As she notes, the "bad stuff" isn't described in great detail.
This is surreal and haunting and wrong and broken and beautiful. I've called it "horror" just for a lack of any other genre to apply; it's also a twisted kind of hurt/comfort.
At night, Sirius’ dreams swell with images of sex, violence and strangulation. Sirius has considered using a knife, but he hates the sight of blood. Strangling would be so much cleaner and he wouldn’t have to see any gore. Unforgivables are just too impersonal for Sirius’ taste. He’s more of a hands on kind of guy. He wants to look his victim in the eye while he’s choking the life out of him.
The light gradually ebbing out of black eyes, pulse slowing into nothingness, body going limp beneath him. If this be madness, Sirius no longer cares.But that's not quite what happens. I was smiling at the turning point and it really
is kind of a happy ending, albeit still in that shattered-mirror way.