So basically continuing the whole Demon Castiel/Dean thing, using different key scenes from series 4-5 as and when I could see them fitting with the idea. Picks up after "Demon Deal" which ends with Sam's return from Hell. Focuses mainly on the idea that Castiel is aware that he is working for Lilith, and has to make sure Sam breaks the final seal (as the angels want him to) by keeping Dean occupied.

Dean holds out a month before he does the summoning spell.

For a while he's tried to convince himself that Sam is back, so whatever was going on with him and Castiel can stop. The only reason for it was his own crippling fear of being alone, without that he has no reason to let the demon back in.

He's lying on a twin bed in a dingy room, listening to Sam shift in the midst of another nightmare. It hits him then that he needs Cas. Not, he requires his help, his insight or his companionship. Because frankly, that's insane. But he needs him, regardless.

Ten minutes later he's outside, ritual at the ready.

The first thing Castiel does is hurl him against the parked sedan two spaces away.

The first thing he says is, "What took you so long?"

A while later they're lying, panting, against the car, Dean propped up against the wheel arch with his shirt and fly open. Castiel is similarly dishevelled, leaning partially against his chest. The demon shifts, turning to face him.

"You've met an angel." It's not a statement, it's a lead in.

"Yeah, Ruby, or called itself Ruby anyway. It's what pulled Sam out of Hell."

"For a reason." His eyes are darker than normal, but not black. He's thinking about something, something he thinks he should say but can't. It's unusual for Castiel to hold anything back.

"What do you mean?"

"Everyone has a reason. For everything."

Dean can't think of anything to say to that. Cold air hits his chest, Castiel is gone.

On the Head of a Pin

Dean stared at Ruby and Uriel. They'd gone insane, quite literally leapt right off the deep end.

"You want me to..."

Ruby stepped forward, placing a hand on his arm, Dean shrugged it off. Through the tiny reinforced glass window of the cell door he can see Castiel. The thing he's chained to looks like a rudimentary star of David. The Devils traps on the floor are out of view but Dean can imagine the angels have taken every precaution.

They want him to torture Castiel. Castiel who apparently knows something about the angel murders, because he's working with Crowley. Crowley who tormented Sam in Hell.

Dean knows Cas is evil. Has been evil all the time he's known him. Hell, it was Cas who got him hooked on demon blood. Castiel killed Bobby.

He still can't do it.

"Dean this information is imperative." Ruby's voice is blank as usual "Under different circumstances we would have approached Sam. He has the experience." Dean feels a spasm of horror. "But your prior relationship makes this..." she struggles for a phrase that's remote enough to not sound sinister.

"More effective" Uriel smirks.

Dean forces himself to accept the facts. No one is coming to help him. The angels don't give a damn how hard this is. If he refuses, and God how he wants to, they'll go to Sam or someone else.

He lets them lead him into the cell. Then it's just him and Castiel.

The demon almost looks surprised.

"Cas." Dean watches him for a moment before turning to the trays of instruments. He doesn't know a lot about torture, but he knows about demons. He grabs the holy water. Castiel sets his jaw. He's not giving anything away here. It's familiar, like every other time they've been together.

"You get one chance here Cas. Tell me what you know about Crowley."

Castiel says nothing, only watches him with eerie fascination, like he's waiting for something.

He takes a knife, runs it through the holy water, some salt. Makes a shallow, smoking cut across Castiel's collar bone. The hiss of pain Cas produces is somehow both gratifying and appalling.

"Tell me about Crowley." Castiel barks laughter, grimacing as the blade is drawn across his chest. Blood runs, steam rises and angry welts spring up in its wake.

"I don't know anything about Crowley" he sounds almost pitying "but...you should know" he lowers his voice, mocking him. "Your angel friends are playing you." Dean doesn't respond, just moves back to the instruments and dunks a silver rosary in holy water.

"And really who isn't these days." Castiel continues, gravely serious. Even though he's taunting him Dean senses he isn't getting any pleasure from this. That alone surprises him.

"Angels, Sam, God...Me" Dean meets his eyes and frowns at the expression there. Castiel is willing him to understand something.

"Surprising." Dean gouges the larger cut and packs it roughly with the drenched beads, then salt, his finger slide over the slick flesh, opening the wound. Castiel throws his head back, choking a howl of pain. "Tell. Me. About. Crowley."

"I. Don't. Know. Anything." Castiel's face is a mask of barely controlled pain and anger. His eyes are black, hair hanging over his face and blood running from his wounds. Dean grabs a flask of holy water, bringing it up to his lips, takes a drink. Castiel's furious eyes turn ever so slightly wary. His voice lowers, grinding with unease.

"What are you..." Dean crosses the space between them and brings their mouths together, hard.

The pain is instant and blinding. The water scorches like hot sand and molten iron, reaching the back of his throat and sliding down. He thrashes and Dean moves away, only to bring another mouth of holy water to his neck. His mouth deposits poisonous caresses to his shoulder, near the cut on his chest and down. He pulls back just after marking Castiel's hip. His mouth is marked with the demons blood. Castiel is sagging against the chains that bind him but still meets his eyes defiantly.

"Tell me." He whispers. "Or I go lower."

For a moment he fears the holy water's robbed Castiel of speech entirely. Dean is suddenly struck by what he's done. This isn't just interrogation anymore. This has hopped the border into something else. The demon coughs blood, spitting it as far as possible. Dean reaches up to wipe the remainder away.

"Cas..." Black eyes slide away from his, a crease forming between them as he looks at the floor. Then, shockingly, he laughs.

"Cas." Dean barks. Something isn't right here.

"The devils trap..." He spits again, grimacing, "is faulty, Dean"

Dean's eyes tick to the symbol, blurred by dripping water, then back to the demon on the rack.

"Someone wants you dead." With a jerk he breaks his bonds and throws Dean into the table of instruments. "Promise I'll stop before then."

The angels don't help. They probably left the second Dean agreed to go along with their plan. In any case whoever is killing the angels, and Dean has a pretty good idea, won't want him to survive.

He lives because Castiel allows it.

What else is new?

The pain of Cas's entry flares with each thrust. He can feel the wetness of blood on his back where the demons wounds are still open. Over him he can hear Castiel's rasping breaths and the curses he's spitting out. The pace picks up and Dean, despite his best efforts to stay still and silent, lets out a strangled groan. Inside of him something catches the force of the impact, pleasure burning white behind his eyes. Every move Dean makes, involuntary or otherwise, is punished by the hand wrapped around his neck.

Dean squeezes his eyes shut as it cuts off his air again. The beating he got was light considering the torture he dealt out. Usually Castiel never hurts him, no more than a deep bite or scratch, maybe a nest of bruises. This is different. Dean stays still because Castiel is claiming back what he's lost.

The violent sounds mashed against his throat become lower, keening sounds. The hand on his neck, loosens, drops down to rest on top of his own, fisted on the concrete. The thrusts become erratic, then slow, as Castiel deliberately reigns himself in.

"Cas..." It's almost choked off, he's too tense for this, for anything more than being used.

"Shhhh" He buries his face in the hunters neck, exhaling softly. The hand that isn't intertwined with Deans reaches underneath his straining body. The sound the hunter makes is wrecked, a strangled sob of relief. Castiel strokes him and slowly thrusts.

"Cas..."

"Dean" The demon nips at his neck, catching the pulsing flesh. He relaxes. Castiel is back in control, punishment over, normality restored. He brings them both off lazily and slumps next to him on the ground, curled against is back.

Dean turns to face him, catches Castiel examining his wounds speculatively.

"Not bad" He rubs a thumb against one of the holy water burns that mark his torso. "Did you have fun?" His smile doesn't reach his eyes. "I had fun."

The Rapture

They find Cas exactly where the answer machine message says he'll be. The warehouse is...well wrecked doesn't cover it. Partially demolished is more like it, Castiel is almost hidden by debris.

"Cas!" Dean shakes him roughly by the shoulder, Sam waits a short distance away. He hasn't seen Castiel since the night he returned to Dean's side. The night he chose to ignore the scent of sex that filled the motel room. Even though he's concerned for his brother, when the demon finally coughs and opens his eyes, Sam's a little relieved. For about thirty seconds.

Castiel jerks violently away from Dean and looks frantically around the warehouse, catching sight of Sam.

"Cas?" Dean looks down on him, realisation and not a little horror making its way into his voice.

"No" The man meets his eyes and he can see the anger there "It's me, Jimmy."

Sam sees this as a good moment to step between the two.

"You're, uh..."

"The guy you haven't been helping for the last year? Yeah, that's me." He gets up, still beaming apocalyptic rage at both brothers. Then he looks away, towards the warehouse door.

"Hey..." Dean steps forward; this guy is the only clue they have to where Castiel's gone. Judging from the half finished Enochian symbol on the ground he can guess who forced him to leave his chosen body.

"Get the hell away from me." The guy backs away, but not before Sam see's the fleeting fear that Dean's proximity creates. For the first time he understands.

"Uh, Jimmy?" Cold blue eyes meet his. "I know that this whole year...I know what possession feels like, so I understand..."

"You understand nothing." He practically growls. "I've been missing for a year, my wife must be..." he breaks off and turns angrily to Dean "So that you, you and the...thing that stole my body, and used it to kill and...so that you can get off."

"I'm..." Dean's expression is the most conflicted Sam has ever seen. For the first time he considers the relationship his brother is in, because after a year it's not really in fling territory anymore. How has he reconciled it? The knowledge that Castiel is using someone, someone alive and fully conscious, to be close to him.

"He told you!" There's an edge of hysteria to the accusing shout. "That bastard told you, and you did nothing."

Overhead the string of hurricane lamps flickers and dies. Jimmy's eyes widen.

"No" it comes out almost a whisper. "No, this is not happening again."

Because he knows what's happening. A year ago, back home, the same blackout had occurred and he'd seen the smoke. A writhing mass of black smoke that choked him and pushed him to a corner of his own mind. Worse than that feeling had been the voice, his voice only different, addressed to the empty room.

"Settle down and nothing bad will happen to your family." Jimmy feels fear somehow, trapped in his own mind. "and that's not a promise I usually make. But these are special circumstances" the voice becomes authoritative. "Be thankful."

More lights flicker in the warehouse, a wind comes from nowhere and stirs the dust from the floor. Sam can't bring himself to help, he's stuck between doing the right thing and wanting his brother to keep the one thing that brings him any measure of peace. Then there's Ruby, the angel that pulled him out of hell and is currently sporting her own stolen body. He can't bring himself to judge Castiel, not for this at least. Jimmy looks from one brother to the other with resignation. The wind picks up.

"You have no idea." His drawn and angry face twitches with private humour. "At least I'm not the only one getting screwed."

Black smoke bursts into the warehouse, funnelling down into Jimmy's body. By the time Castiel is fully in control, Sam is gone, leaving Dean to it. Cas blinks, looks around and then focuses on Dean.

"You're back."

"Dean..."

"No, just..." his face screws up in disgust. "Take him home and get back to hell." He looks the demon in the eye. "If I see you again, I'll kill you myself."

Lucifer Rising

This is admittedly what he would expect of a waiting room for heaven.

Shame he's a little distracted by the fact that Sam's off somewhere trying to take down Lilith, alone. Ruby's standing on the other side of the room. She won't take him to Sam or let him speak to him. The angels have closed ranks. They're going to let Lilith break the final seal.

Right after she kills his brother.

"Dean" Ruby's expressionless voice comes from behind him and he flinches. "I know this is difficult, but it must be done." Zachariah, chapter one, verse two.

"Do you wish for me to leave?" Dean very nearly says yes, almost shouts at her to leave him the hell alone.

"Bring Cas here."

Silence.

"Castiel." He clarifies. "Can you bring him here?"

Ruby looks at him for a long moment and then vanishes. Just long enough for him to doubt she'll return, she does. Castiel is with her. He's still wearing Jimmy Novak, but his clothes are different. Same coat, black suit and a slightly cleaner white shirt. Grey tie. Castiel notices the direction of his gaze.

"He changed them, when I sent him home."

"Course he did." Dean feels rage uncurling in his stomach. Castiel takes a step towards him, his brow creasing in an urgent frown.

"Dean, Sam needs your help..."

"I know!" The dam breaks, maybe it's seeing Castiel again or just that he's confirmed his fears. "I know, She knows he's coming, Cas, he doesn't stand a chance against Lilith..."

"Lilith is the final seal." His voice is dead, cold.

"What?"

"Lilith is the first demon, the final seal on Lucifer's prison. When Sam kills her, the cage opens and the apocalypse will start."

"You knew" Dean's fist connects with the demons jaw, it has no noticeable effect but it makes him feel slightly better. "You knew the whole time and you didn't tell us."

"I tried." He practically growls, eyes flicking black for a second. His shoulders sag. "I'm sorry."

"It's the end of the world Cas, you need a better word than sorry." Silence hardens around them. Dean feels helplessness crawling around inside him, Sam is somewhere else freeing Lucifer because the angels lied to him, to them. At this point the knowledge that Castiel has been lying since day one is a welcome distraction.

"So, this must have been fun for you, right?" Castiel cocks his head to one side, his questioning look grates against Dean's nerves. "Being up here, Lucifer's man on the inside. Hell you even had me believing it."

"And you swore to obey Heaven." Castiel's face twists in revulsion but his voice remains soft, urging Dean to understand. "You sent me away. Do you have any idea..." Somehow he's gotten closer, too close. "You wanted me to let Jimmy go? I did. For the last month I've been between here and Hell, not a nice place to be." This is the first time Dean can remember Castiel being gentle, but he is. His hands resting on Dean's waist, eyes flicking over Dean's face.

"Lucifer is our God, Dean...he..." He closes hi s eyes, shakes his head. It's too complex to explain here, like this.

"Yeah, well, looks like you'll be seeing him soon."

"Don't bet on it." Cas's lips meet his, the closest they've ever come to reverent. Something presses against his hand. He pulls away, glances down. It's a knife.

"Cas..."

"Lucifer can take hell on earth, and shove it." A slight smirk ghosts across his face, the words aren't his they're definitely Dean's. "Because I see nothing but pain here; I see inside you, I see your guilt, your anger, confusion...and it's just not doing anything for me. I think you were right, I'm just not demon enough."

The room trembles slightly, a sure sign that Zachariah is on his way, Dean grips the knife and cuts his palm, quickly etching a sigil onto the wall. His hand hovers over it as he glances back at Castiel.

"I do this. We'll both be hunted, they'll probably kill us."

"They'll try."

It end's badly, luck of the Winchesters, Dean isn't surprised. After Castiel got him to the convent he lost track of him. Sam had already killed Lilith, Lucifer's prison was gaping open. By the time he starts looking for Castiel it's too late. Demons hate traitors as much as anyone else, Castiel's been taken back to Hell.