Title: Our Mark

Author: xascasfellx

Rating: M

Pairing: Dean/Castiel

Spoilers: Promo for 9x23

Word Count: 3,126

Warning: Major Characters' Death

Cas can feel his Grace—not his own that is—dying inside him. It withers away as the seconds pass by, and soon—too soon for his own good—it will die within him, taking Cas with it. He knows this and possibly he should be okay with it, actually he is, only, Cas doesn't want it to happen so soon. There are too many things he wishes to do before he dies for good this time. Too many things he has to say. Most importantly, too many moments he needs to share with the one man he gave up everything for, and will continue to give up everything till the last ounce of Angel is sucked out of him. He just wants a little longer so he can save Dean from this dark hole he is drowning in. If only he could save Dean, then it would all be worth it. Yet, Castiel knows it is too late.

Every day he is with the hunter, he sees the light being taken from his green eyes. Everything that once made Dean happy is just useless now, because the only important thing in the world to him is blood.

Death. Destruction.

He is no longer the man Castiel has fallen for—in every single way possible. He is no longer his Dean.

The Mark of Cain is taking Dean away from Cas. Every blood thirsty second that ticks by is another second that leads Dean to the demon he is sure to become.

If only Cas could save Dean from himself.

The only thing he knows he can do is be there for him till it happens, and try to find some way to keep his hunter with him.

Castiel has never been one for foolish positivity. He is a realist. And the reality of the situation is—Dean will lose his humanity and will become a demon, and Castiel will burn away with his stolen Grace, and Sam will lose the only two people he has left in life.

Because life isn't a fairytale. There are no happy endings, this Castiel has learned all too well.

And most importantly, this time, there will be no second chances.

Castiel sits solemnly in his leather chair in the library, watching the bookshelves, not really sure why he can't look anywhere else. It's not like there is much to do for him at the moment. He has no army. He has two hunters who are too broken to be any use, and a former Angel on Metatron's side dying in the guest room just down the hall. He has nothing to do but to wait. He waits to see what will become of his hunters, what will happen with Metatron, and Gadreel.

Waiting.

Waiting for the seconds to tick by till the end. And as he waits, he will stare at a stack of books without thinking to pick one up.

Somewhere behind him, he hears Sam trudging into the bunker with speed that only notes he is running. A hand, Sam's hand, comes down on his shoulder, spinning him around to face him. He is sweating to the point of his long hair sticks to his forehead and the sides of his neck in soaking clumps. His eyes, much like his mothers, are wide in panic and hold so much of his past that it is hard to read what is bothering him at this moment, and not what haunts him from before.

Cas is about to ask but Sam beats him to it with a loud, harsh voice that sends his nerves on edge.

"Dean—he's gone. He broke out."

…..

An Angel and Hunter walk into a bar—it sounds like a bad start to a worse joke, only it's not a joke, it's their life. Castiel walks straight up to the bartender, whom is eyeing Sam from afar, as he asks around about Dean. For some reason, without seeing directly into the girl, he knows this is where Dean would have come, she is the type of girl Dean would have hit on. As much as Cas wants to dwell on his jealousy he can't. Right now, Dean's safety and the safety of every human that comes into contact with him is more important.

She smiles sweetly at him, making Cas avert his eyes. She is rather beautiful. Dean should have been here. He holds up an old photo of the hunter so she can get a good look at him.

"Have you seen this man?" He can hardly make out his own voice with the noise in the bar, and the throbbing in his ears. The Grace is beating inside him.

"Sure, he came in here not too long ago. Don't tell me he is in trouble. He seemed like such a nice guy." Castiel ignores the flirtatious way of her voice and focus's in on the fact that he was here. Not too long ago. He will find Dean and he will make sure he is okay, because Dean is the only thing that matters to Castiel. Always has and always will.

"Do you know where he went ma'am?" The girl rubs back her blonde hair from her eyes, and looks around the room a little before focusing back in on Castiel.

"He said something about Dallas. Maybe there?" He doesn't give the girl another look, only turns around to grab Sam's shoulder and pulls him from the bar. He needs to find Dean. Now.

…..

"Why would he be in Dallas?" Sam asks from behind the wheels of the Impala. Dean hadn't taken his car, maybe because he knew that Sam and Cas would have found him easily had he taken it, or that he was too out of it to care how he got to his next kill. The latter was more likely, though he wishes it wasn't.

"This isn't Dean, Sam. He is capable of anything at this point. The Mark his driving him to kill. It's coursing through his mind, taking over every instinct he has. It's only a matter of time." Sam doesn't say anything else for the rest of the car ride, nor does Cas. There really isn't anything to talk about. Both of them want to get to Dean as soon as they can. Both are worried out of their mind about him. Yet neither one can say out loud what they know they will have to do if they found him drenched in an innocent persons blood, because the truth is, neither will have the strength to do what needs to be done.

…..

After two more stops to two other bars, and two aesthetically pleasing women later, Cas and Sam roll up to an abandoned canning factory on the border between Texas and New Mexico. Dean has been jumping around from state to state, and their last lead sends them here. From the smell of blood, and feeling of dark power, Cas knows Dean is in there. And he knows what they will see when they find him. It is almost enough to make Cas run away so he doesn't have to come to terms with what happened. He felt it. About an hour ago when they were sitting in the silent car, Cas felt the charge of power coming from Heaven. He felt the release and the whispers of his brothers and sisters. He knew it had been done.

Castiel would have been happy about it, if it hadn't come down to this.

He follows behind Sam with caution and as slowly as he can so he doesn't get there to see Dean in the state he is in.

A girls scream come from the end of the hallway. It is enough to make Cas flinch. He feels sick, and not just because the Grace is tugging at the life left inside him. It's not too far now. Actually, it should be soon.

Castiel increases his speed to make it to Dean in time, ignoring the excruciating pain that stabs him in the temple, almost knocking him over. Not right now. Not this moment. He needs more time. Just more time to get to Dean.

When Sam breaks down the door into one of the old employee working areas, Dean looks up at the pair with solid black eyes, the color of his soul. They are too late. It's all over. Cas steps forward, only to be knocked down with a sudden flash of pain to his abdomen. He feels Sam's hand on his back.

"Cas?"

"I'm fine. Dean—" He quickly gets to his feet and composes himself into the person he needs to be right now. "Dean, put down the knife." The person who once was his friend stares back at him, still holding The First Blade to a young girl's throat. She has blood covering her face, making it hard to see her characteristics, only that she is looking at him with utter fear, begging them to help her.

"Dean," Sam says slowly, holding out his hands to show he holds no weapon, taking minimal steps towards his once brother. Dean doesn't react in anyway. From the corner of his eye, Cas sees a red light shining from Dean's arm. The Mark is throbbing in time with Cas' deteriorating Grace. They move together in time. One killing its victim, the other giving him life, a dreadful, horrible, dark life. Another round of pain shoots through Cas' head, making him let out a yelp that makes Dean's hold on the girl loosen just long enough for Sam to knock away his grip on the blade. Dean lets out a growl that is in no way human, lunging for his brother. Cas blocks Dean's attack by throwing himself in the way, letting the hunter lay on top of him with both hands wrapped around his neck. If it wasn't for the stolen Grace killing him, it wouldn't have hurt in the slightest. Cas holds onto Dean's shoulders, one hand where he had marked Dean all those years ago, looking deep into those soulless eyes, pleading for him to come back.

"Dean—" He hears Sam again, and the girl muffled crying, but the only thing he can concentrate on is Dean. His face curls up into a snarl, baring his fangs that stand out there. He has changed. He will never again be the man he once was. Even if he somehow got through this Mark, Dean would never live with taking the life of so many woman. He wouldn't want to. With his last amount of energy Cas could give Dean peace. Cas couldn't stand to let Dean eat away at himself anymore. Only if Cas could summon up the strength to.

"Dean please, come back to us. Please—" His voice lets out a scream at the end as another round of stabs take their toll on his temple. Dean's hands loosen around his neck, his face softens. "Dean, I need to you to come back. I need—" Black spots covers his vision at the edges, till he can almost not see Dean's soft features. His freckles that Cas had wanted to kiss a thousand time. His scar that stays at the base of his chin. Every little thing that made Dean, Dean was starting to fade from Cas' vision. "Come back to me…please." As if being yanked out of a trance, Dean stumbles away from Cas gasping for breath. He claws at his head, almost breaking his skin in the process. Once Dean is off of him, Cas can regain his sight and moves quickly towards him.

"Cas…Sammy—" Dean screams till nothing comes out, a few unholy growls coming through. He is here, but just barely. Cas turns to Sam, who is standing back grasping at the girl that won't let go of him. He has tears streaming down his cheeks. In that moment he only sees Sam, the man who wanted to go to college and wanted to marry the girl of his dreams, wide eyed and lost. He sees the baby brother Dean was brought up to protect. How could he leave Sam alone in the world? How could he be so cruel? He looks back at Dean who now is scratching frantically at the Mark.

"Dean you need to come back. Leave the mark behind. Come back to me." His voice is frantic as he tries to get through to the hunter. Cas reaches Dean, pulling him towards his chest, embracing him, more to deal with the explosion of agonizing pain that comes from behind his eyes, than anything. Dean grasps at his back, fighting for control.

"Cas!" He screams. Cas holds on for dear life to him. For if he lets go, he lets go of Dean. The one man he's fallen for. His human. He can't ever let go. Another blast causes a whimper to come from Cas' lips. "What have I done? What have I done!" He sobs without tears, probably looking behind Cas now to the injured girl he tried to kill not minutes earlier. Castiel pushes Dean arms length away from him, making sure to keep some grasp on him. "I'm losing. I can't—agh!" He drops into Cas' arms again, pulling them to the ground. Only Cas keeps them upright, holding Dean strong in his arms. "You have to do it. Cas you have to do it for me. You pro—agh!—promised! Kill me!" Dean's words hang heavy around the room. Only nights before, right after they locked Dean deep in the bunker, he had. Dean had asked him to stop him by any means necessary if things had gone too far, Cas had promised. He had promised because deep in his mind he had some hope that things would never come to this. Now that they have, he needed to do what was right. He needed to kill Dean Winchester.

Castiel slides the Angel's blade down his arm, into his hand. He pushes Dean away from him. Blood soaks his face, almost like a mask. He can only make out two perfect green eyes, begging, pleading for it to end. For him to end it.

"Cas please!" He screams. Only his voice is heard. Distantly he makes out Sam screaming back at them. He holds it grayly wanting nothing more than for this to be a nightmare, one in which he will wake up as a human, next to Dean, normal, perfect Dean. He wishes he didn't have to do it.

As much as he wishes, Castiel knows he has to. Now. Because in a few minutes, he himself, will be gone. His stomach burns with the Grace ejecting itself. He grips tightly on the cold metal of the blade, thinking for a moment about jabbing it into his own stomach to just end his own life. He looks back up at Dean who is clawing again at The Mark, black patches overcoming the green in his eyes. He's changing again. Only a matter of time before the demon takes control.

"Dean—I can't—" He startles himself by saying it. All this time, all these years of choosing Dean over everyone, Castiel doesn't anymore. He chooses himself. And by doing so, he can't kill Dean, he won't. Even if that means breaking his promise. He will never hurt him again. Because he would rather the whole world go up in flames than to have to watch the life die out in Dean's eyes, demon or not. He chooses love.

"You promised me you son of a bitch! Just fucking kill me!" Dean stagers forward towards Cas just as another shot of pain makes him double over. "You promised me you'd kill me! Kill me Castiel, damn it just kill—" It all happened so fast he didn't process it for a moment, only knowing that Dean was centimeters from his face, breath cold on his tear soaked skin. One minute Dean was walking towards him as he felt his Grace beginning to leave, and the next both of their abdomens were soaked in blood—Dean's blood. Castiel holds the Angel blade in his hands, while the other end is stuck deep within the hunter's stomach, his hands holding desperately on Cas' shoulders. His mouth hangs open in the shape of a circle, his eyes glassed over. Cas feels himself screaming before it reaches his ears. He hears Sam's screaming overtop of his own.

Lowing them both to the ground, Cas holds Dean's head onto his lap. Tears mixed with blood fall on the hunters face as he looks up into Castiel's fading grey eyes. He can feel himself slipping along with Dean, for he had just killed his reason to live. Fuck God. Fuck humanity. Fuck everything else of this damn planet, Dean Winchester is the reason Castiel hasn't stabbed himself with his own Angel blade long ago, and now, he pulls it out of Dean's stomach watching the light fade. Dean looks up into Cas' eyes, as Sam comes to their side, cupping Dean's cheeks in his hand. Cas can't even bare to look at the younger Winchester. He had killed his brother.

"I'm—" There's a gurgling sound and some blood coming from Dean's mouth now. "Sorry—" A light, much like the light of an Angel's, flashes through Dean's eyes, nose and mouth, blinding and beautiful. He feels it. He feels him. His soul is pure and good, everything Dean was—is. He feels love washing over Sam and himself. He watches Dean's face as his soul soars to Heaven where it belongs. He hadn't had the chance to save him. He had killed in return.

As the light begins to die down around them, Cas feels lethargic, he feels the weight of the world, and his sins start to take their toll on his used vessel. Cas sways in the air, lightheaded and unaware. He hears Sam say something, and feels wetness on his cheeks. Just as the last bit of his Grace leaves his body, Cas falls, falls towards the one he's always fallen for. He rests his head gently on Dean's chest, not caring that there is blood there, not wanting to think about it being Dean's. Castiel's eyes roll in the back of his head, time and time again, before he feels it.

He feels Dean calling him.

He feels Heaven.

He feels God.

Just as he closes his eyes for the last time, head where it was destined to be, hand wrapped around his mark on Dean's lifeless shoulder, Castiel looks up at Sam Winchester for the last time and whispers, "Thank you."

Everything turns to darkness.