Blood
When you wake up in the dark, back pressed up against a hard concrete wall, the taste is still on your tongue. Fear and horror grips your heart until you realize that the blood in your mouth is your own and that tonight you didn't give in to the wolf's hunger. You can't see anything in the pitch black, but from the smell, you recognize it as one of Hogwart's hidden passageways. Someone is running soft fingers across your body, tracing the long open wounds that mar your skin and the claw marks that run down the length of your chest, like the signature of a monster-lover. You grab Sirius' wrist harshly and hiss, You shouldn't do that.
You don't need to see his face to know that he's shocked, but that's because he thinks this is a game. Every night that you change is another night for him to chase you down, to catch you and then drag you back as if you were his prize. He doesn't realize the blood he's getting all over his hands just by touching you could really hurt him, that it's the blood that changes you and the blood that makes you who you are.
He's tense for a moment, lying next to you, but slowly you feel him move over your body and this is Sirius' way of placating you. He thinks that whatever's wrong can be solved by his mouth at your throat and his hand on your cock, and you let him think that because he needs you to need him. When he tries to kiss you, you turn away because the blood in your mouth isn't for him. It's for the wolf, and you quickly swallow it before consuming Sirius, mouth hungry and wanting.
You're gasping and clawing, arching your back as you feel him push inside of you and his hot breath against your ear. Remus, he whispers over and over again, but it's a name you don't recognize.
Don't, you tell him, don't call me that. Call me by my real name.
And maybe Sirius understands you better than you think, because he chokes out Moony like it hurts him to say it, but he does it for you. You grab his ass and push him deeper into yourself, hissing at the pain and reveling in it at the same time. Your elbows and the heels of your feet scrape against the rock floor, and the wolf in you smells the blood seeping out, screams for more. Sirius' blunt teeth biting at your lips aren't enough and you push against his body harder, faster, fiercer, until you let out an animal cry as you come.
Sometimes you remember. Bits and pieces push through the haze and you can still taste the blood in your mouth. Human blood, metallic and salty. As much as it horrifies you, the wolf in you craves more and you can feel him simmering right below your skin, watching the world through your eyes and howling at the four walls that keep you trapped. He wants the moon, he tells you, he wants the cold air, the dangerous open fields, the dark forests. He wants blood filling his mouth and blood drowning his heart and blood pulsating through his veins to a rhythm only he can hear: faster, faster, faster.