That is fuuuuuuuuucked up! Deliciously dark, but man! It made me squirm... all that blood, and those knives. I enjoyed it, though, in some perverse way... which is a little alarming, and it was so well written; I felt as though I was there! *shudders*
It would be interesting to read what happens when Snape *does* come out of his mental state, and whether Remus will be able to revert to more 'normal' behaviour.