All You
"Do it. It's all you."
That's what Sam remembers when the blood hits his tongue, spilling bitterness down his throat in a crimson flood. He hadn't meant for this to happen. Even when he'd had the chance he'd stayed his hand, unable to bring himself to slash the throat of the thing that once - still - was his brother. But in the end it hadn't mattered.
Dean had been on him the minute that he lowered the blade, pinning him to the wall. Anger blazed in his eyes that Sam had been too much of a coward to do it, as his hands closed in a stranglehold around Sam's throat. He'd take what he wanted one way or another.
Sam's vision began to swim until all he could see was ink black eyes leering above him, and then he felt the knife leave his grasp as Dean pried it from his weakening fingers. He was barely aware of what was happening as Dean dragged the blade across his own wrist, and then suddenly the pressure on his throat was lifted.
There was only one brief moment of relief, leaving him gasping and choking for air, before he felt something wet and cold being pressed against his mouth.
Sam's breath caught, trying desperately to turn his head away as the blood trickled past his lips. The scent of it filled his nostrils, and with a sickening feeling growing inside him he realised that this was what Dean had wanted: for him to use the blade all along. Make him bleed.
Even after all this time it hadn't lost its potency. The blood was intoxicating, making Sam's head spin and his senses sing. It was taking every last drop of his energy to refrain from just opening his lips and letting it spill inside, the long dormant beast rising within him to slake its thirst for demon blood.
Dean knew how hard it was for him resist. Even though Sam struggled, tried to pretend this was being forced on him, by the time he opened his mouth and latched onto the cut bleeding freely from his brother's arm, he knew that Dean had been right. This was all him.
It's still all him as he devours the crimson elixir like a man in the desert gulps down water, holding Dean to him rather than letting himself be pinned down. It's been so long and oh how he's missed this. He hadn't even realised how badly he'd needed it before, but now that he has it, he doesn't know how he went without it for so long.
The blood is bitter on his tongue: all acrid sulfur and iron as he swallows it down, but he's never known anything sweeter. It's hot: not the warmth of a living body, because Dean is like ice, but brimming with the heat and power of Hellfire that floods his veins and makes him feel more alive than he has in years. He can taste the Mark in Dean's blood, and it's purer than anything he's ever had with Ruby or any demon he can remember.
Dean is cradling his head now and stroking his hair as he murmurs, "Drink up, little brother." Sam hates himself as he realises what Dean is doing and surrenders himself to it. Even now Dean still can't stand to be alone and he's going to damn Sam with him.
Sam never meant to give in so damn easily, but he does. Because he knows now, he can taste it in Dean's blood, that all the darkness and pain that had festered in his brother's heart and twisted his soul wasn't something put there by the Mark. That was all Dean.
And now with the sweet poison spilling down his throat and blackening his own soul, Sam knows it's all him too.
