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Tainted

Summary:

As his nightmares get worse, Dean realizes he’s turning into something he’s terrified of; he needs his girlfriend’s help. The corruption of the Mark of Cain leads to a heart-wrenching promise. Can the curse be lifted or will it leave scars?

Notes:

Demon!Dean and MOC!Dean hold my heart. I've been wanting to write an angsty fanfiction about the Mark of Cain arc for a while now, and the Jacklesverse Bingo 2024 Challenge on Tumblr has inspired me to finally go for it. I haven't written a multichapter fanfiction in years, so I'm both nervous and excited. This is a longer project, bear with me.

Crossposting on Tumblr

Listen to the playlist.

(See the end of the work for other works inspired by this one.)

Chapter 1: Practice My Confession

Chapter Text

The clock's digits stared back at him, mockingly so — 4:06 AM. Their glow matched the same crimson shade that had originally startled him awake.

He was still breathless, too, after jolting up into a rigid, wide-eyed state.

Every fiber of him felt as if it was made of stone. Lifeless, cold, paralyzed. Everything except his heart, anyway. That part of him defied his stillness, hammering relentlessly against his ribs and threatening to leap into his throat.

Squinting, he averted his gaze by lowering his head. Reluctantly he blinked down to his hands, which were trembling in his lap. Though his clammy palms felt sticky and cold, a pang of relief washed through him when he realized it was simply sweat that was sticking to his skin.

He had half expected to see the blood still.

Just a nightmare, then.

Those weren’t anything out of the ordinary for Dean Winchester. The man had spent more sleepless nights in his life than he’d ever had the luxury of a full night’s rest.

However, this one was different. It was raw. Violent.

Last time his tormented slumber left him this hollow and shaken was years ago — back when the memories of Hell were still fresh in his mind. Even to this day, seven years later, the times of fire burning flesh and endless torture sent shivers down his spine. But it’s been a while since his dreams were this vivid.

The soft rustling of bedsheets pulled him back to reality.

“Dean?” — Her voice was thick with sleep and laced with concern. Just mere moments ago she had been fast asleep. Peaceful and calm at his side, grounding him as always. Except he was still unable to shake it off.

This feeling, which was just as attached to him as the symbol embedded into his skin.

“Hey,” was the only lame reply he could muster. Even the movement of his mouth felt askew and wrong. “Sorry, did I wake you up?”

Instead of replying, she reached towards the nightstand, flicked on the lights and sat up. Dean remained perfectly still at her side, his eyes still glued to his trembling hands.

That was until her hand entered his field of vision. The second he understood her attempt of grabbing his hands, he pulled his away. His shoulders stiffened further as he cleared his throat.

“Just a nightmare, ‘m fine,” the hunter grumbled, more to himself than anything, whilst swiftly swinging his legs over the edge of his side of the bed. He rubbed his palms up and down his thighs thrice, then ran his wiped hands through his messy hair only to realize his forehead was just as sticky with sweat.

Even with his back turned towards her, quite a literal manifestation of the impenetrable walls he liked to build around himself, she recognized the gravity of his ‘nightmare.’ His shoulders were slumped yet tense, and the way he avoided not only her gaze but also her touch caused her stomach to churn.

Right away she understood this was about more than just an unpleasant dream.

She watched in silence as he got up, barely making out the mumbled word “shower” as he slipped into the bathroom.

Part of her wanted to follow after him, just to make sure he was okay. As okay as he could be, anyway.

They’ve all noticed how on edge Dean was lately. Not that anyone blamed him for it, given the stressful nature of the past few weeks. Defeating Abaddon has taken a toll on Dean, more so than any of them wanted to admit.

They could’ve never killed a Knight of Hell without the Mark of Cain.

However, it became more and more obvious that the strings attached to this curse were heavier than originally anticipated. Desperate times had called for desperate measures. But seeing Dean slip away from sanity more and more made her question whether it was really worth it.

Ever since killing the demon, his temper became unpredictable.

Even his appetite had diminished as of late, shocking both Sam and her when he downright refused to order a cheeseburger at one of his favorite fast food spots. Furthermore, Dean’s patience ran thin lately, his recent behavior during cases increasingy reckless — if not downright suicidal. He’d charge into the enemies’ nest, guns blazing, just like that and without regard for any possible dangers.

Not to mention, the frequency of those nightmares have reached an all time high, a new record if you will. It wasn’t just the usual disruption of his four hours of shut-eye either; these were the kinds of nightmares that had him instinctively reach for the gun under his pillow, nightmares that left him giving up on going back to sleep at 4 AM.

She would’ve asked him to open up to her, but she knew that would be like talking to a brick wall. Whenever she’d test the waters, he’d dismiss her and avoid awkward conversations about his feelings.

Still, it was worth another try.

As she listened to the water running in the bathroom, she decided to slip out of bed as well, despite her own fatigue. Grabbing her fluffy robe and putting on her slippers, she used the small time window to head to the kitchen. Since it was the middle of the night, the bunker was eerily silent, every step of hers echoing off the bleak walls.

Once in the kitchen, she grabbed a kettle and two mugs, brewing up some tea. Something to warm and soothen those nerves of Dean’s. For good measure, she added more ingredients to both cups, then walked back to their shared room.

She kicked the door shut behind herself just in time for Dean to leave the bathroom.

Dean only stole a brief glance in her direction, before he sat down on the bed again, back leaning against the headboard. “You didn’t go back to sleep?”

“Figured a cup of tea would do us good,” she shrugged, crooked grin on her lips. She handed one of the cups to him and maneuvered herself to join his side. “Roiboos-Orange.”

Dean sniffed at the steaming liquid.

“Not to sound ungrateful, sweetheart,” he sighed, already moving to hand the cup back to her. “I don’t think I’m in the mood for a tea-party.”

“That’s a shame, ‘cause I even added the special secret ingredient,” she replied with a feigned pout and fished a small flask from the pocket of her robe, wiggling it in front of him. The quiet sloshing of rum inside indicated the bottle’s half-empty state.

Dean paused, then choked out a weak chuckle. Convinced, he brought the cup to his lips and took a sip. Behind the sweet aroma, a spicy note lingered, which admittedly did fill him with some warmth, at least.

“Bribing me with drinks now, huh?”

“Only for the special occasions,” she mumbled and went for a sip of her own cup. Normally she didn’t like endorsing Dean’s drinking habits, but she could tell he needed something to steel himself. Deseperate times, and such.

“Special occasions,” Dean echoed. He sure didn’t like the sound of that.

“I’m not gonna beat around the bush,” she sighed, her fingers closing around the warm ceramic as if she could brace herself for a heavy conversation that way. “Your nightmare, what was it about?”

Unsurprisingly, silence followed.

With great effort, Dean stared at the golden colored mixture in his hand. He focused on the swirls of steam emitting from it, along with its herbal scent. Clearly, he didn’t want to talk about it. Then again, he knew better than anyone that he couldn’t bottle it all up forever.

Then, Dean took a big swig of the warm tea, deeming it to be his liquid courage.

“Abaddon,” he vaguely answered at last.

“Abaddon,” she echoed, skepticism obvious in her tone. “But… you killed her months ago, Dean. She’s no longer a threat, right?”

“Right,” Dean hummed and allowed his finger to circle the rim of his cup. “She isn’t.”

At that, her brows knitted together in confusion. Admittedly, she didn’t understand what Dean was hinting at. If he wasn’t anxious about Abaddon, what else made him so skittish?

“It’s the Mark,” he gruffed through a strained voice, and he definitely did feel his throat close up, no matter how often he’d try to swallow the lump inside. “It’s this burning sensation, I— it felt good, killing her, you know?”

She remained silent at his side, listening with increasing confusion and tension.

“Because we had to defeat her,” she nodded in agreement, but Dean shook his head and she saw him clutch the cup until his knuckles turned white around it.

Clearly, she didn’t get what he was saying. Not at all.

Dean paused for a moment, unsure how to put it into words. Killing Abaddon hadn’t been a task of necessity. It had been one of urgency, the personal kind. He needed to kill her, yes, because every fiber of him had demanded it.

Because he wanted to do it.

“Because it was satisfying,” he corrected her with just a mutter under his breath, barely audible, as if he was ashamed to admit it. “The First Blade sinking into her was just, well, powerful. It was like scratching an itch.”

He stared ahead, blankly. Even in the dim light of their bedroom she saw the green of his eyes being swallowed by something dark and cold.

“It keeps replaying in my dreams, me killing her,” Dean mumbled.

He remembered every detail of it, even though at the time it had felt like he had just blacked out. Impaling Abaddon smoothly, her pained scream melting into her last breath, him stabbing the lifeless body again. And again, for good measure.

And again, and again, and again.

Sam had struggled to make him snap out of it, to make him drop the First Blade.

The familiar voice of his girlfriend reeled him back from the flashbacks. “You did what you had to do,” she reassured him, but he knew that it wasn’t as easy.

“I kill other demons in my dreams, too,” he continued, clearing his throat. “Tonight, I dreamt one attacked you and I just… I snapped and I ripped him apart. I’m talking limb after damn limb, severing sinew and muscle and tearing flesh from every fucking bone, until there is nothing left but pulp.”

It was the way he said it that sent cold shivers down her spine.

It was not as romantic as it may initially sound, not when his hands were twitching, jaw clenched and eyes filled with a sinister bloodlust. That was what it was all about.

The Mark of Cain was singing a siren’s song, calling for violence. Demanding bloodshed.

She knew her boyfriend would do anything to protect her. He’d kill for her in a heartbeat, without regret, if it meant keeping her safe. After all, Dean Winchester was known to be ruthless when it was necessary.

But was it really about fighting for her, or was it about ripping the enemy to shreds?

Dean’s small ministration — him scratching mindlessly at his lower arm where the Mark was embedded, burnt into him like a scar — told her he was after the latter. After the thrill of gutting foes like animals and drawing enough blood to quench the curse’s thirst.

It was an unsettling thought, both for her and for Dean.

They had already seen the darkness that came with the Mark of Cain, but the real grasp it had on Dean suddenly seemed much more terrifying.

She, too, remembered seeing him practically slaughter Abaddon.

But she also remembered him taking back control, and she knew he still held the reigns.

What he needed most now was trust. And she did trust him, with her life, always. Mark or not. So she reached for his hand for the second time this night. This time, her fingers grasped his wrist successfully, gently but firmly, and she pulled it away from his arm so he’d stop scratching the Mark.

“It was just a dream, baby.” Despite her greatest effort, there was a slight tremble in her voice.

Her eyes searched his green ones and she saw the turmoil within. The look of exasperation.

He was so tired.

“You don’t get it,” he huffed, his voice breathless and broken. “I enjoyed it.”

Was it about vengance? Maybe.
But even more so it was about the sheer simplicity of it. The twisted needs falling into place so perfectly whenever, dream or not, he’d sink a knife into flesh, crack bones and drain as much blood as possible, until it was hot and sticky on his hands.

The Mark craved it, corrupting him slowly but surely into madness. It was constanty calling for him to do unspeakable things, even now.

It demanded him to kill.

“I’m scared of what I’m capable of,” he whispered through a strained voice and squeezed her hand, clinging to her like his life depended on it. “In that nightmare, you were just gone and I… I couldn’t control it. I just saw red and it felt so fucking real.”

Without hesitation, she reached over him, placing her cup of tea on the nightstand on his side and adding his right with it. With both of her and both of his hands free now, she interlocked their fingers together.

“It wasn’t real,” she reassured him. “You can control it, you always did.”

Dean took a shaky breath and scoffed. So far, yes, she was right. But what if one day he’d fail and lose his composure? He felt like he was hanging on by a thread. And he was way too weak to hold on for much longer.

He was slipping. He knew he was. It was only a matter of time.

His voice was so defeated, weeks of exhaustion weighing down heavily on him: “I don’t want to find out what I would do if I lost you.”

Those words were a stab to her chest. She didn’t even know what to reply with. No words could console him, she felt just as helpless.

“We’ll find a way to get rid of it,” she whispered, but they both knew she couldn’t promise something like that.
They could try, and they have looked into just about everything. But it was a losing battle, honestly. There wasn’t much lore on Cain, much less on the curse and how to remove it.

“No,” Dean sighed, shaking his head. “No, ‘cause if not, then— I don’t want to hurt anyone.”

“Dean—”

“You have to stop it,” he interrupted her. “If things go to shit— when they go to shit, you have to stop it. Stop me.”

The invisible stab-wound in her chest froze to solid ice. He was talking as if he had already given up on a cure. Was it so wrong to still have faith?

“Nothing will go to shit,” she insisted, letting go of his hands only to cup his face instead. “Look at me. We won’t let you down like that, you know that, right?”

He regarded her words for a moment, but the silence between them was heavy and the despair palpable.

“Promise me you’ll put an end to it if things go wrong,” he spoke, begged. “Please.”