Blood.

It was blood that had caused all this. Sam sat on the grungy thin carpeting of the motel room, his back pressed to the door, and studied the blue cords threading under his skin. His blood. It was why Mom was dead. Why Jess was dead. No. Not dead. Murdered. Mutilated.

Sam's mind ran through the list of names, of relationships, of worlds destroyed because of his existence. Because of that warm thick liquid running through his veins. He traced a finger lightly over the steadily pulsing branches as he recited the litany. Mom. Jess. Dad. Dean. Jo. Ellen. Adam. Gabriel. Castiel. That werewolf chick in San Francisco—Madison, right? God, how messed up was it that he couldn't even remember all their names? Hell, he didn't even know all their names. There were hundreds. Maybe thousands. The fucking Apocalypse.

And some of them... Sam shook his head at the thought, brow furrowed in introspection. Some of them had even died more than once. Castiel. Adam. Dean was back, but that wasn't because of anything Sam had done. It was because Dean was better—he was the strong one, the right one. The one Sam had betrayed.

Sammy imagined himself tearing the veins through the thin skin, blunt nails bloody as they ripped through flesh. He had guns, but that would be quick. He didn't deserve quick. He deserved pain. Penance for his sin of being born. Without him, the demon would never have killed Mom. Without Mom dead, Dad would never have taken to the road, become a hunter. Dean would have had a normal life, Dad wouldn't have had to sell his soul—hell, wouldn't have even known how.

Sam leaned forward just far enough to pull the silver knife out of its hiding place in his boot. He ran his finger along the blade. He held it up to his eyes and examined the shine of the razor-honed edge with a detached morbid fascination that had become all too familiar. The cool metal felt incongruously soothing as he pressed it against his wrist, a whispered possibility of one final round of pain before blissful peace.

He didn't press down. Not yet. Not. Yet. But as the polished tip scraped lightly up his arm Sam could see his death reflected in the pools of blood he'd left in his wake. He scoffed.

Blood.

It all came down to blood, didn't it? The demon blood fed him as an infant, corrupting him in ways he still didn't understand. The blood of everyone he'd ever loved, spilled for his sake like a mockery of the crucifixion: they had died for his sins, they had suffered for his crimes, they had bled for his damnation.

And, G-d, the blood he'd consumed willingly—eagerly. This is my body you eat. This is my blood you drink. Every drop consecrating his service to that darkly shining Morning Star that hunted him and haunted him. That would eventually possess his mind and claim his body and raze this literally G-d-forsaken world. Finish what he'd started. Everyone was so sure he would say yes. Of course they were.

The metal of the blade had warmed now, thick red fluid thud-thumping steadily in its fragile confines so nearby. Just a little pressure. A little pressure and a little time. And that traitorous blood would slip from his body and he would slip with it—slip on it. Slip and fall away. Fall into Hell and the torments he deserved.

Something childish and indignant rebelled at the thought and Sam's anger flared. Despair was overtaken by frustration and he coiled in on himself briefly, letting the tension pull him tight, before he brought himself back up to straighten his spine against the door. He forced deep bitter breaths of stale second-hand air into his lungs. Why did he deserve this? He didn't choose to be born or bastardized or bent into a weapon of celestial battle. He had never wanted this life; had resented the idea of being his father's pawn long before he had realized he was a piece on a much bigger chessboard. It wasn't fair!

But the fight fled quickly. Because he was old enough and jaded enough to take "life isn't fair" far more deeply to heart than anyone he'd heard utter the phrase had ever intended. Because he knew that while he couldn't fight his origins, he could have controlled his actions. Because Dean had told him...

Dean.

His only blood left on Earth.

Sam could still see and hear the pain and anger and betrayal that shone from his brother's eyes and shook from his voice. So many times. Disobeying their father, running away from "home", leaving for Stanford, having visions, using demonic powers, allying with a demon—it was getting to be hard to remember ever having done something right. Disappointment was all he ever brought to anyone. And now, after Dean had seen that little Sammy's slice of heaven was anything that got him away from the dysfunctional mess that passed for their family...

It made Sam stop with an almost physical jerk. Huh. The knife was almost forgotten now as Sam tapped it against the heel of his hand while he explored this new thought. It had almost broken his heart when his older brother had dropped the amulet in the trash with the remains of his hope. It clanged with a volume and finality that far outsized its physical mass. But Dean hadn't thrown it away after Lucifer had been released—no, the truth now: after Sam had released Him—or after they had failed to kill Him. No, what had bothered Dean more than the prospect of the End of the World was... what? Losing Sam? But he'd driven Sam away more than once. Of course, each of those times, hadn't it been Sam who had left and Dean merely told him to stay gone?

Dean didn't drive him away. He called him on his bullshit, sure. Named him in that phone message as the vampire he'd become, sucking life and goodness from everyone around him. Dean had said Sam deserved to be hunted, needed to be put down and Dean was right.

But… Dean hadn't done it. So many times when Dean could have killed him, should have killed him: when their father had first ordered it, when Sam had been possessed, when Sam had been infected with the Croatoan virus, when Sam had been revealed as Lucifer's party dress, when Sam had fucking started Armageddon.

Dean.

Dean had gone to Hell for him. Literal, blood and guts and fire and pain for eternity Hell. To bring him back from the dead. And he hadn't done it in ignorance. Dean had known their father's warning and The Demon's plans. He couldn't have known just how bad it would get, but he'd still….

Dean saved him. Every time, whether Sam wanted it or not, his brother came through in the end. Every. Time.

Sam looked again at the knife in his hands and almost smiled. Maybe he did—it had been so long he didn't think he would recognize the feeling of the expression on his own face. He pulled his hand back and flipped it forward, sending the knife spinning until it embedded itself in the opposite wall.

Sam knew he would let his brother down time and again. He knew he could be counted on to make the wrong choice at every turn. But that didn't matter. If past is prologue, it went both ways: Sam knew Dean would always make it right.

This was easier. Trusting Dean was something Sam knew how to do because he'd been doing it since he was six months old. They didn't need to believe in G-d or trust angels. Dean didn't even need to believe in or trust Sam. It was probably better if he didn't, really.

But Sam knew Dean; had faith in Dean. Sam had enough faith for the both of them and the angels besides. Sam would look his own colossal flaws full in the face and keep going. If he was a monster he would deal with it later when he had time for self-laceration. The pain and death he deserved would wait until the world was saved. It would wait until Dean succeeded.

Sam levered himself to his feet taking strength from a knowledge no one else—including Dean—had: Sam's blood tangled him in evil, but it also tied him to Dean. And Sam tied Dean to the world.

Dean would save the world to save Sam.

Dean would win. Sam would be there. For Dean.