I mean it. Don't read this if you're easily offended. It takes the characters of the Sonic universe and twists them, and it does as realistic as possible. Drugs, sex, and other heavy stuff are involved. If you're still here, well...
It's a great dark fic. The characters are believable and the story always puts you on your edge, especially after the first few chapters when you don't actually know if what you're reading is real or not. Knuckles has never been exposed this way, and you can come to love him or hate him throughout everything. As Sonic, and Tails, and pretty much everyone named.
If you can wrap your head around Sonic characters being used in a dark, moody and seriously mature way (As in, it may look childish if your worst experience in life is your girlfriend dumping you last weekend, but after you grown up a bit, it can affect you. It can even remind you of your life, or someone's else), you're in for an awesome Mind Screw Dark Fic
beautifully written, full of emotion and all those things you've come to expect from good darkfics.
If you can't... well... you can always go back to play the games. They're much more happy.
Seriously, Shadow the Hedgehog is kid's stuff compared to this.