This is honestly one of the creepiest and most brilliant fics I've ever read. And I've read a lot of creepy and brilliant fic (though not often together).
It had me screaming at first (my longtime OTP is Lily/Severus, by the way, and Snarry does not appeal to me at all), but I kept reading, and your writing got better and better, and yeah. I really enjoyed it. It freaked me the hell out, but it's very well done. I also liked the wealth of potions detail through it - very impressive. I love it when authors creatively and realistically build on canon magic.