I sort of hate myself for writing this. Just a little.
It's set directly after "Stairway to Heaven," because I really needed to react to it...
WARNING: Contains Wincest, dark!Dean, and dub-con. Also something like a happy ending.
Castiel ran with Gadreel minutes after they got Dean restrained. Clapped a hand onto the shoulder of the wounded angel, spread invisible wings, and disappeared. He didn't take the First Blade with him. Sam alternates between resenting him fiercely for leaving the weapon in Dean's possession, and sympathizing with him. The latter is when he believes that Castiel is afraid of the power that the Blade represents, and what he might be tempted to do with it. He doesn't want to become what Dean is turning into. Sam can understand that.
"I'm going to get help," Castiel told Sam, in his urgent, gravelly voice. He was steadying a reeling, dizzy Gadreel, who was gasping like a fish out of water (even though angels don't need to breathe) and pawing weakly at the long slash on his chest. Sam hadn't hated him since Dean beat him to a pulp, and he felt sorry for him then. "Someone who can fix this. I'll be back."
Sam didn't really believe it then, strong arms wrapped around the struggling, snarling form of his older brother. And he definitely doesn't believe it now, since two weeks have passed without a whisper from anyone at all outside the bunker. There's only Sam, and Dean, and a whole lot of empty space. Sometimes Sam thinks that the world may have quietly ended out there, leaving them as the last men alive, drifting through space in their sealed bunker. It wouldn't surprise him.
Sam could leave. But Dean won't let him. He forces him to stay here, never even opening the door, and though that gets under his skin like a hive of fire ants, he thinks that he might like it a little, too. It's sick. Sure it is. If Dean still wants him here, though, Dean might still need him.
Every dictator needs something to rule. Without that, they're nothing at all. If Sam knew for sure that he could unmake Dean by leaving him, he might risk running. But he's too afraid that he'll go and it won't make any difference at all.
Dean made good on his claim that "this is a dictatorship," as soon as Castiel was gone. He wrestled himself free, and started roaring at Sam. Tearing him a new one. Ordering him around. Sam was furious, he was scared – he roared back, that turned out to be a mistake, because Dean cut him. He only used the tip of the Blade. One ancient tooth tearing flannel and cotton and Sam's skin, scratching a shallow line on his bicep, and it hurt more than Sam ever knew that anything could. He was no stranger to pain, but this was something else. Fire scorching the veins closes to the cut until it felt like they should have been tubes of brittle glass, muscles spasming, nerves shriveling up into frail little tangles.
But the worst part wasn't the physical aspect. The pain shot from the cut straight to his heart, and he felt Cain's guilt, Abel's fear, Cain's grief, Abel's confusion. It brought him to his knees. No wonder Gadreel had been panting.
Dean's eyes were hard when Sam looked up. He didn't help him off the floor, and he didn't have regret anywhere in his expression.
Sam got to his feet and went looking for Metatron in the library, just like Dean had told him to.
His brother had never hurt him before. Not when he didn't deserve it. Sam was even more afraid than he'd been before, and more of that was for Dean than for himself. Dean is strong, noble. Or was. He went through life with ten tons of guilt that he hadn't really racked up. The Blade has stripped all of that from him, and left behind a razor-edged monster. Maybe it's even stripped away his love for Sam, which Sam knows is the only thing that has kept him moving forward at times. Now the urge to kill seems to have replaced it as the driving force behind the thing that is Dean.
Sam understands addiction. The need for a substances that makes you feel powerful, in control of your life and what it's doing to you. Dean's savagery brings to mind his own, right after he was done lapping sulfur-tainted blood out of an open vein, or the grooves of a rune-carved knife, or the dirty palm of his own hand, even though Dean gets his fix just by holding the Blade. Sam also understands detox. He would tie Dean up, away from his stash, if he could. He'd even handcuff him to his bed and listen to him howl until he's clean. Dean did that for him once, after all. No, Dean did that for him twice.
But Dean doesn't sleep very much anymore. Or at all, really. His green eyes are feverish, the stubble on his jaw silvery. He sits and stares at nothing sometimes, slowly turning the handle of the Blade over and over in his hands. Sam watches from where he's hunched over a bundle of disorganized files or a pile of ancient books, thinking of the rope and handcuffs that he keeps under his bed these days, wonder if this was how he looked to Dean when he was haunted by the memory of Lucifer.
And Dean always has that damn knife with him. All the time. He eats, teeth bared, with one hand, and keeps the other wrapped tightly around the Blade's grip. He taps the teeth of it absentmindedly against his thigh while researching. He spins it casually between his fingers as he walks from room to room in the bunker. Sam tried to take it away from him after a week without Castiel, wanting to get him to set it down. Just for five minutes. And Dean cut him again. Across the face this time, opening a shallow cut on one of his prominent cheekbones.
He collapsed again. He screamed. When the pain faded and he forced himself to his feet, Dean was gone.
It was a few more days before Sam realized that, at the moment, he's more to Dean than just an extra pair of hands to help with research. Not much more, granted. Sam began to understand, when Dean woke him from a fitful sleep by climbing onto his bed and dropping a heavy hand onto his waist, that what the Blade does is turn you into an animal. Like Sam had been without his soul. You didn't care about anything but combat, revenge, and killing. And sex.
Even without his soul, something in Sam had still shied away from Dean. Maybe because he was missing key parts at that time. Sam had been lustful when he jumped into Hell; he was in love when he was brought back out. Apparently, there had been nothing between those times.
Dean kept holding the Blade against him as he buried a hand in Sam's hair and jerked his head up so that he could suck and bite at his lips, as if afraid he'd struggle. Sam didn't raise a finger against him. He had wanted this for years, though he never once found the courage to tell Dean. Desperate, twisted love, the need to feel his older brother's hands on him, a hunger for everything in Dean that he himself will never have.
Not like this, something in him cried out as Dean's hips began to move and the Blade pressed, cold and foul, against his stomach. No. I don't want it like this. They were both still fully-clothed, but Dean seemed unable to ignore his need for release any longer. Please…do it right. Sam had wanted Dean to undress him slowly, showing him a rare gentleness as his eyes glide appreciatively down the well-muscled body of his younger brother. Kiss him in dim light, roughly murmuring how much he loves him, and work him open slowly. It was dark here and Dean never said a word.
When Sam's not thinking about Castiel, he wonders if Cain raped Abel before he killed him, or if they made love as tenderly as they knew how.
Sam didn't talk, either, that first time. He rolled over. He spread his legs. He yielded, eyes fluttering closed and a pleading puff of air slipping out of him every time that Dean touched him. It was crude, sure, impersonal, but it was still contact. And Sam moaned when he felt Dean come, shuddering and growling, after rutting against the denim-clad curve of his ass for ten minutes. He would have reached for him when he got up and left. He didn't have to come himself – they could just lay together in the dark. But he was afraid of being cut again.
He thought that, maybe, Dean would never strip his clothes off. Just use him because he was better than grinding into a memory foam mattress. Dean penetrated him the next night, though, dry and harsh. He was still using Sam's body to masturbate – it was just more intimate now. Sam helped Dean get his pants off. Being used is better than being ignored, or killed because he's in the way.
And Sam lives for the little moments that come right after the little moments that come right after Dean is finished fucking him, when he's worn out from coming in his ass and the Blade hasn't sunk its fangs back into his mind yet.
He still holds it during that time, though. Of course he does. As he thrusts rhythmically into Sam's red, abused opening, his hand moves on the grip like Sam desperately wishes it would move on him. He can't help but watch that. It makes him sick, makes him ach along his spine and somewhere deep in his chest, just like when he watched Crowley inject human blood. It's a reminder of how weak he once was. And this is also a reminder of the fact that his big brother has succumbed to the very same weakness.
Today has been a very good day. By Sam's new, laughably-low standards, at least. Dean hasn't cut him, they found what may be a lead on Metatron, and three spit-slick fingers were shoved up inside of him right before the usual cock. So it was easier, for Sam to lift his hips and take Dean. It hurt less. He groaned, just like always. Dean never reacts to the sounds that Sam makes, but it's better for Sam if he pretends that they're making love. That his De isn't basically raping him because he needs an outlet for the Blade's brutal nature.
Sam pants, as he rocks with Dean's movements. The teeth of the Blade brush against his upper arm. Through obedience, he has earned the privilege of no longer being threatened with it while Dean works himself to orgasm. He hates how he feels like that's an achievement. He hates the First fucking Blade so much that, soon, just the sight of it in Dean's callused hand will make him vomit.
He's on his back tonight. First time. Dean suddenly rips almost fully out of him, and Sam gives a little, gasping cry of pain, blinking back tears. He's so raw. He's never cried before during sex, or bled, but there's a first time for everything. He has no idea how Dean would react if he burst out crying. He has no real desire to find out.
Sam used to touch Dean, a little. His hands, whenever they came into range. Dean always jerked them away. Lying on his back, Sam keeps his hands to himself as the pain fades into a low, steady burn. Even though his position would make it so easy to reach up and spread his palms over Dean's freckled chest, play with his dusky, erect nipples, run his fingers through his dirty-blonde brush cut.
Once, he touched the Mark, and that's why he has a cut in the small of his back. It was so hot that blisters rose on the tips of his fingers afterwards (he popped and bandaged them by himself), and he felt something squirming inside of it.
Sam thinks about stroking his own cock, as Dean's slides back and forth inside of him. He decides against it, though; he doesn't want an orgasm. Dean, on the other hand, is getting close. Sam can tell by the way that his breathing changes. He tickles Sam's prostate as he thrusts, but never hits it just right, because he never makes an effort to.
Sam clenches, and Dean snarls as his seed spills inside of him. Sam closes his eyes, sighs softly. It's disgusting, but he likes the hot, silky feeling of being full. Of his brother's come. They're both monsters.
Dean slows, stops. His breathing is deep and ragged, and Sam can feel him shuddering with exhaustion and aftershocks. He hangs above him, silently, for a few moments. Sam opens his eyes when a feather-light touch falls onto his chest.
Dean is stroking the soft, sparse hair between Sam's pectorals. Sam breathes steadily, looking up at him, noting how some of the fever-brightness seems to have faded from his eyes.
He reaches up, and lays a hand over Dean's. He squeezes it, feels it press deep into his chest as Dean moves his other one. He touches the cut on Sam's cheek, which has not healed, only gone red and puffy and sore, and he's so gentle that the tears come back. Sam can feel the love that drove his brother to sell his soul in the gesture. He closes his eyes and shivers as Dean moves down to run his fingers through his hair. It isn't for several moments that he finally realizes what that means.
Dean is not touching the Blade.
And Sam would reach for it, but he doesn't have the strength as Dean kisses him, guiding his lips open and seeming to lose himself in Sam's flavor. His eyes ache, now, with the strain of holding the tears back. He is worth something. He is loved. He lifts his arms and pulls Dean to him, because this has never happened before. He's never kissed him, and Sam forgets all about the Blade, because he suddenly has his brother back.
He forgets, until Dean abruptly breaks the kiss and grabs the Blade. He pulls out, he dresses, and he's gone, after telling Sam he'll come and get him if he needs him. Sam doesn't cry. He curls up into a ball on his side, even though it hurts the cut on his back, and touches his lips. The cut on his face tingles.
"You're still there," he whispers, knowing that Dean will never hear him. "I can bring you back. You're still there.
Sometimes, Sam wonders if, after Cain and Abel coupled, Abel had to beg Cain to let him go, to save him. Because feeling Abel against him brought Cain back to himself.
He wonders if Abel wept in Heaven, watching his brother wither away into a demon. A monster.
If he would have done anything different, had he had the chance to.