It's different than the first time… in ways Dean can't even begin to put into words.

For one, this time he hadn't just killed a couple thousand people. But it was more than that.

As Dean felt another hot pang of electricity resonate in the mark, he wondered absently if this feeling would lead to its own withdrawal. He couldn't bring himself to care; there was nothing that could convince him to give up this feeling.

He had to appreciate how gracefully Cas managed to scuff his shoe to break the devil's trap without pulling away from him at all. As soon as he felt himself released from confinement he swung Cas out of the circle. He shoved him roughly into the small table, jostling his laptop and knocking a book to the floor.

Dean cupped his hand around Cas' head, fingers sinking into his hair. He paused, a sly smile working onto his lips. "You're not going to punch me again, are you?"

"We'll see how things go."

"Mmh." Dean didn't have time to react before Cas flipped him around with dizzying speed, and he sucked in a breath as he landed half on top of the table. He took the opportunity to slide up to sit on the edge, one hand shoving the contents off to the side and out of harm's way. He pulled Cas closer to him, his knees squeezing in to trap the angel's hips.

The hunter was still trying to grasp and define exactly what was different. It was a little difficult to think given the circumstances. He hardly noticed that he followed Cas' lead up and off the table.

This time doesn't feel desperate. Dean thought, feeling like he had nailed it. Then again-

Dean felt his head bounce off the wall when Cas pushed him back again. He caught the angel's shoulders. "You're not careful and you're going to break those wards after all." He warned.

Cas frowned, stopping for a second to consider that. He closed his eyes as he felt Dean close the gap between them again, a hand sliding up his chest. He let out an involuntary shudder before changing tactics.

Dean steeled himself to hit the upper landing hard when Cas spun him out and threw him at it. He was instead surprised when he came up against an invisible force, as if there was a wall there. His mind spun as he realized Cas had effectively pinned him to a wall that had no bearing on the structure of the cabin whatsoever. He almost opened his mouth to compliment the ingenuity but it was cut off before he could start.

Cas braced his forearm across the demon's chest, the new position leaving him no choice but to support himself on the demon. He bent into the contact, letting Dean control him for only a second before he threw his weight to the left. Dean was caught off guard as Cas swung back over the salt line just out of reach.

Dean blinked a few seconds, but before he could say anything Cas was back, just barely. He was distracted by the returning taste of Cas' lips, but he realized what was happening. The angel now had complete control again and metered out how much of him was Dean's to take. The hunter watched him smile. Fucking smile.

"That's no fair." He breathed as soon as he was allowed air again.

"Tough."

Dean couldn't help the grin of his own, and he returned to take whatever he could get, craning his neck up to take Cas' lips again, the stair giving Cas almost three inches on him. He waited for his opening.

As soon as Cas made the mistake of reaching out to grab his shirt, he caught Cas' wrist, pulling him forward and through the salt line, tipping him off balance. Cas inelegantly caught himself on Dean's chest, impressed with the fluid motion that righted him and slipped under his coat at the same time.

Somewhat annoying. Dean admitted to himself, continuing to work out how exactly this felt. He was avoiding half the things he wanted to do, in the interest of keeping the cabin in one piece.

Definitely better than killing Cain. He concluded.

Dean was almost amused that they ultimately ended up sprawled on the floor in front of the fire. He looked over to try to get a read on where Cas' head was, flinching slightly on reflex after how their last sexual encounter ended.

Cas however was just relaxed against the small rug, arm casually over his head, his hips turned towards Dean. His eyes were closed, more relaxed than Dean had ever seen before.

The demon grinned, pushing himself half upright for a second, extending his arm and just managing to knock loose the two throw pillows. He flopped back onto the floor, stuffing one under his head and rolling Cas against him.

Cas readjusted himself slightly, settling down across his chest.

"You know, I can think of a few things to add to that supply list if we're going to make this a regular thing."

Cas smiled gently. "I'm sure you can."

Dean blindly groped behind him until his hand met the soft fabric he was looking for. He tugged the blanket up and over both of them.

Cas let the last remaining shred of tension out of his shoulders.

"And I do think we should make this a regular thing."

The angel hummed what Dean took for an agreement. He ran his fingers back and forth across Cas' back. He wondered absently if Cas could feel the touch in his wings, or if they were just entirely out of phase with everything around them. He almost asked, but decided against it. "We should probably shower." He ran his hand up a little further, just brushing by Cas' neck, soft enough to cause goosebumps. "Another group activity."

If he didn't know better, he would say Cas' tone shifted towards disappointment. "There is hardly enough room for one person in that shower."

Dean sighed. He knew Cas wasn't wrong, but he really wanted him to be.

"I'm not in a hurry to move anyway." Cas concluded, absently rubbing his hand over Dean's rib cage. He was quiet for a minute. "I do not know if I am willing to ask your brother for any of the items that might be on your list."

Dean grinned. "I guess I'll just have to ask him in person."

.

That evening in the bunker, the library was quiet despite the five people pouring through texts. The silence was uncomfortably thick, and almost everyone jumped when Kevin stood up. "I think I might have found something." He skimmed over his notes again. "It's a spell for containing an angel."

Sam frowned. "Dean is already contained."

"No, not by just trapping them… by cutting off their grace entirely."

Charlie shook her head. "So?"

Sam shook his head. "So without access to the traces of Lucifer's grace, he's just a demon."

"Well, probably still an immortal demon, because of the mark." Kevin admitted.

Crowley leaned back in his chair. "Still. He'd be susceptible to most demonic spells."

Sam looked at Rowena. "Is that true?"

"Aye." She said slowly. "And with that out of the way, it should be far easier to build the rest of the spell."

Sam let out his breath. "Okay. What do you need?"

"Right now? A glass of wine and a complete translation of the spellwork used to unbind Hera."

Charlie looked up, making a face at Sam and subtly nodding towards the hallway. She got up and headed out without saying anything.

Sam waited a minute before he stood. "You keep working on it. Let me know when you have the next piece." He followed Charlie to the kitchen.

She leaned back against the counter, crossing her arms over her chest. She spoke in hushed tones, wary of being heard down the hallway. "Hey, are you sure about trusting her?"

"Yes…" He paused. "For now." he clarified.

"Because you made a deal with her." Charlie prodded. "And what was that exactly?"

"She doesn't expect payment until it is done." Sam evaded. Rowena had recognized that they needed Crowley to gather what they needed for the spell.

"Comforting." Charlie scoffed. "And once you do?"

"We hope we never see her again." Sam shook his head. "I know it's risky, but it's also the only move we've got. She's contained, Crowley is holding up his end of a deal. And we're actually making progress." He stressed.

Charlie sighed, walking a few steps and sinking down onto one of the table stools. "What then?"

"What, after we remove the mark?"

She nodded. "What happens to Dean then?"

"We turn him back… make him human again. That's all we can do."

"You think he'll be okay?"

Sam closed his eyes. "I think it'll be a while… but yeah. I think he can come back from it. He came back from Purgatory… came back after hell…"

Charlie had read. But she had also read Dean's greatest fears before hell. It wasn't the torture, it was becoming a demon. And now he had… twice. He'd killed thousands of innocent people. He nearly killed Cas…

Sam interrupted her thoughts. "What choice do we have?"

Charlie's breath caught in her throat. "Yeah." She relented, letting out another sigh.

.

Cas had been asleep for several hours when Dean found himself pouring a cup of coffee. A hold-over from his time pulling all-nighters as a human. Now it served no purpose but habit. He listened to the gentle sounds of Cas breathing from the other room. He smiled gently. He suspected Cas had decided to keep the door open in the hopes that just the sound might lend any scrap of calm over the mark.

"Hello Dean."

The former hunter startled, sloshing hot liquid in his mug slightly, the voice to his left entirely unexpected. He whipped his head to the side, coming face to face with Death himself. He narrowed his eyes at the horseman before they widened slightly, and flicked towards the bedroom door.

"No. I didn't come for him. We need to have a little chat." He clarified, his voice its usual conflicting tone of indifferent annoyance.

Death walked over to the kitchen table, casually tossing a bag onto the table. "Bacon cheeseburger, from a small dive bar in Missouri." He said simply, reaching in and extracting one before pushing the bag Dean.

Dean hesitated before he reached for his own. He gave it a quick glance before taking a bite, hesitating before nodding his approval. He relaxed slightly. "What do you want?" He asked through a mostly full mouth. He was careful to keep his voice down, not wanting to wake Cas if he could help it.

"It's well past time we talk about that thing on your arm."

Dean's brow furrowed, and he looked down at the mark. He swallowed "What, this? What has this got to do with you?"

"Word around is that Sam is trying to rip that thing off of you, whatever the consequences."

"Yeah. Key word so far is trying." Dean said slowly, still not following. "And?"

"And you and your brother have no idea of the consequences we're talking about."

Dean rolled his eyes. "Let me guess, you're here to tell me."

Death leveled a glare on the hunter that silenced him. "Creatio ex nihilo…God created the earth out of nothing . Or so your Sunday-school teacher would have you believe."

Dean crossed his arms. "What, so Genesis is a lie? Shocker."

"Before there was light, before there was God and the archangels, there wasn't nothing. There was the Darkness, a horribly destructive, amoral force that was beaten back by God and his archangels in a terrible war. God locked the Darkness away where it could do no harm, and he created a Mark that would serve as both lock and key, which he entrusted to his most valued Lieutenant, Lucifer. But the Mark began to assert its own will, revealed itself as a curse, and began to corrupt. Lucifer became jealous of man. God banished Lucifer to Hell. Lucifer passed the Mark to Cain, who passed the Mark to you, the proverbial finger in the dike."

"And?" Dean said flatly.

"And if you and your brother manage to rip that mark off your arm, the lock is broken and the darkness is set free."

Dean stared at him. "How bad are we talking?"

"A far greater evil than any of us have ever known."

"Awesome." Dean muttered. "So, what are my options here?"

Death took a long drink before continuing. "You could simply give the mark to someone else." He said passively, knowing it wasn't even a consideration. "Or I could make sure you would not be a danger to anyone on earth."

"You mean, you'd kill me."

The horseman looked like he was having his patience thoroughly tested. "With the mark on your arm, nothing can kill you, Dean. Not even me."

"So what then?"

"I could relocate you somewhere, far from this earth, where you would no longer be a danger to anyone."

Dean just stood there for a moment. "Not on this earth? What, Pluto? Farther? Yeah, okay." He snorted. "What is my third option?"

"Live with it."

"Live with it?"

"You cannot remove it, lest the darkness be set free. Your options are to take yourself off the board entirely, or simply learn to handle it as Cain once did."

Dean snorted. "Yeah, that worked."

"You have your options. Now is the time to pick." Death's focus sharpened on him. "What will it be, Dean?"

"Yeah, I'm going to stick with the one that doesn't involve a one-way trip off this planet."

Death regarded him for a moment, cold and unblinking, half silhouetted by the light of the fire behind him. "Very well." He got to his feet, taking a few steps towards the center of the cabin before turning around. "You have to stop your brother, Dean. Now." And with that, he was gone.

The demon stayed frozen for a moment, catching up. He finally shook himself from it, striding across the cabin with purpose. "Cas!" He demanded, standing as close to the edge as he could.

Dean heard the breath catch in the angel's chest as he was rudely pulled from sleep. "Cas, get out here right now." He fought the urge to pace, forcing himself to stand still, breathing against the mounting frustration.

Cas looked around blearily, trying to make sense of Dean's voice outside his door. He finally managed to shake himself, kicking off the blankets, and getting up. He left his coat, just walking onto the upper landing. He stopped, taking in Dean's agitated appearance.

"Give me the phone."

Cas squinted at him, still not quite fully awake. "What?"

"The phone Cas, now."

He didn't argue, hearing the urgency in Dean's voice. He walked into the bedroom and emerged a second later with the device.

It was dialing a second later, and he heard Sam's greeting on the other end.

"Sam, stop what you're doing." Dean ordered, his voice low and urgent.

"Dean, where's Cas." Sam demanded.

"Sam listen to me, You don't know what you're messing with. So I need you to stop fucking with the book and leave it alone until you talk to me."

"Where is Cas-?"

Dean growled, rolling his eyes, He hit speakerphone and held it up. "He's right here, happy?"

"Cas?"

"I'm here Sam."

Sam tried to make sense of what his brother was saying. "Cas, what's going on?"

"I don't know."

"Damn it, Sam! Death spoke to me. You're fucking with things you don't understand, and if you don't back down a whole lotta people are going to die."

There was silence on the other end as Sam tried to process what was being said.

"Sam, are you hearing me!?"

"Dean, I don't know what to do with that."

Dean furrowed his brow, his posture tensing up. "What the hell do you mean 'don't know what to do with it'? You stop, that's what."

"You want us to stop. You don't want to be cured."

"This is not what this is about." Dean growled, his fists clenching as he tried to restrain the anger brewing inside. "Just leave it. For now." The demon took a deep breath. "Just until you come talk to me, okay? Just hear me out."

Sam was silent for a moment. "Cas?"

The angel was keeping a wary eye on the agitated hunter, slightly worried he was about to snap. Dean looked sincere, but Cas knew he wasn't good at telling whether he was lying or not. "I don't know."

"Oh fuck you." Dean snapped. "Sam, you listen to me. I don't give a rat's ass what you think my angle is, you stop what you're doing and you come here and listen to what I have to say, you owe me at least that much. You don't like what you hear, skip on back and have a party, but I am telling you, a matter of life and death, stop what you're doing."

There was another pause before Cas spoke up. "Sam… I think you should listen."

The younger hunter let out a breath. "Yeah… alright." He finally relented. "I'll be there in the morning."

"Thank you." Dean hissed, ending the call and tossing it back to Cas without warning.

Cas fumbled, but caught it. "Dean, what's going on?"

"What do you know about the darkness?"

.

Sam closed his eyes, well aware of the eyes boring into the back of his head.

Kevin frowned, watching him for a moment before speaking up. "It could be a trap." He said softly, putting voice to what everyone was thinking. "If he knows we're getting close."

"Yeah." Sam agreed. "That's what I'm thinking."

Charlie frowned. "So what do we do?"

Sam debated with himself for a moment, but he really couldn't get away from the suspicion. "I'm still going out there." If nothing else, he wasn't going to leave Cas alone with Dean right now.

"What do we do?" She pressed.

Sam made up his mind and looked back at them. "Keep working. And if you figure it out, do it."

.

"So when you say they fought-?" Dean was now pacing back and forth across the cabin floor, much like he did during his withdrawals. Cas was impressed that he somehow seemed more agitated now than he had then.

"All four archangels and my father went to battle against her, and were victorious." Cas tried to keep his voice gentle, despite answering that question for the twentieth time.

Dean kicked at the magazine holder as he walked by, scattering volumes across the floor that he carelessly stepped through a moment later.

The six hours until dawn had proved to be an exercise in how much Dean could ask for and how many different ways Cas had to say he didn't know.

"And now?"

"Well, lacking God and any Archangels might be a problem." Cas said, not quite managing to keep all of the exasperation from his tone. He shifted slightly on the couch, trying to fight off another wave of exhaustion as he watched the hunter keep moving.

Dean didn't notice. His head snapped up as he heard the distant rumblings of the impala's engine, and instantly tensed. He didn't wait for Cas to do it, instead walking over and into the repaired devil's trap, anxious to start this right away.

Sam gave a half knock before opening the door, taking stock of Cas before he turned to check Dean was restrained.

"Sam-" Dean stopped when the younger hunter put his hand up.

"I'm here, happy?" He ignored Dean's sour expression, walking over to where Cas was just getting to his feet. "You okay?"

"I am fine." Cas said. "Just tired." He really wished potentially catastrophic consequences could wait until a more reasonable hour to arise.

"He's fine, now can we talk?" Dean demanded.

Sam sighed. "What is this about?"

"Death paid me a visit last night." Dean repeated their earlier conversation. "He heard you were trying to remove the mark."

Sam shook his head. "And?"

"He was pretty insistent that it was a bad idea."

"And you were the only one who saw him?" Sam cut in before he could continue. He looked back at Cas. "You didn't see him?"

"Damn it Sam, are you listening to me?" Dean fought down the static that was building in the mark, successfully for the moment.

"What else did he tell you?" Sam asked flatly, not yet believing this was anything other than an elaborate attempt to avoid being cured.

"He said that this was given to Lucifer, then to Cain. That this is some sort of key or whatever holding back the Darkness."

Sam noticeably paled at the word key, but he recovered quickly. "What does that even mean?"

"Well, what does it sound like? Does it sound like a good thing?" He shifted, crossing his arms. "He said it was 'A far greater evil than any of us have ever known'." He quoted.

"He didn't get more specific than that?"

"Not really, Sam. I pretty much think that summed it up." He nodded to Cas.

Cas stepped forward. "Sam, the Darkness was a force present before the onset of creation. God could only build this universe once it was contained. It took the combined efforts of him and all four archangels to trap her." He watched Sam's expression. "I never mentioned it before he asked."

Sam furrowed his brows, feeling a spark of concern, but pressing on anyway. "Dean, how do I know you didn't just read this in a book? I have no way of proving you even spoke to Death."

"For fucks sake."

"We're getting close and all of the sudden you've got some vague big bad that Death came to warn you about. Just you. With no witnesses." He shook his head. "How the hell do I know you're not making this up?"

"I am not making this up." Dean hissed through clenched teeth. "I am asking you to stop."

Sam squared his shoulders, doubling down on his point.

Cas stood a few steps back, listening to the two brothers as their argument quickly escalated. He hoped in vain that perhaps one or both of them would tire, and the volume would drop back to a level he could rejoin without having to spend the effort to scream. He could see where Sam was coming from, but Dean seemed genuinely unnerved. He tried to figure out how he was going to say that.

Two states away, four people hit the bunker walls following a violent release of power.

Cas was the one who noticed it first. He looked down at the back of his hand, noting the hairs standing up on end, and he felt the charge ruffle through his concealed wings. "Guys."

"Stay out of this Cas." Dean snapped, eyes never leaving Sam.

"Dean. Sam." Cas insisted sternly, throwing them a look that left no room for argument.

Both brothers fell silent. Dean shuddered as he too finally felt the charge in the air. He whipped his head up to glare at his brother. "You didn't stop." He accused.

"Dean-"

He was cut off by a deafening crack, the air around the mark seeming to spark to light, and Dean grabbed his arm, crying out at the sudden searing pain.

Sam moved forward on instinct but Cas clamped a hand on his shoulder, pulling him back slightly. He watched the demon carefully.

The mark burned hotter, clearly resisting the blatant attack. Dean sank to his knees, feeling the acid spread from his forearm up over his shoulder, slowly winding its way across his chest. He clamped his mouth shut against the scream, tasting the coppery tang of blood as he bit his tongue. The light flashed green for a second and then fizzled away, leaving a small arcing trail of electricity and then nothing but clear unblemished skin.

Dean sank to the ground, panting as he slowly regained control of his body.

Cas didn't let go of Sam, holding him firmly in place. Sam frowned. "Dean?"

Dean groaned. "I'm okay." he grunted, pulling himself onto his knees. He took a second before he pushed himself up to stand. He looked up at Sam, eyes turning black. "You couldn't leave it alone for one freaking day?"

Sam had the good sense to look unnerved. "We were too close."

"Good job Sammy. I'm cured." Dean spat. "If the world dies bloody, this is on your hands. I warned you."

Sam's reply was cut off by a low rumble, the ground beneath the cabin beginning to shake. The lantern on the table rattled until it fell, glass shattering on the wooden floor. Logs fell from their stack, pots and pans crashed together inside the pantry.

Outside the wind picked up, ripping around them so violently it blew the tarp covering right off the door. The windows shook in their frames, cracking slightly between the earthquake and the gale outside.

Dean looked up and around them. "Let me out." He demanded hurriedly, standing right up at the edge of the devil's trap.

Cas didn't wait for Sam to catch up, he simply dove forward, scraping away the paint.

Dean wasted no time. He reached down, dragging Cas back to his feet and beginning to haul him backwards. He reached out a hand, grabbing a fist full of Sam's shirt, pulling him nearly off his feet towards the bathroom. He shoved them both inside, looking back into the space behind them as the walls themselves began to groan under the pressure. He slammed the door shut,sliding the bolt closed.

Cas looked down at the locked door. "What are you-"

"Small space." Dean said, having to practically shout to be heard over the noise. "Stronger."

Sam put a hand up to shield his face as the small window in the bathroom finally gave way, sending shards of glass flying into the room.

In the distance he could see strands of black, violently swirling and reaching up from the ground, gathering into one giant wave. "That's-"

"The Darkness." Cas said, almost too quiet for any of them to hear.

Dean reached sideways without thinking, grabbing onto Cas' hand and holding it tight. He got one last look at those blue eyes before the inky smoke reached the building and plunged them into the black.

The last thing he heard was Sam shouting his name.

End of Season 10. Thus begins Season 11.