Wow this took me a long time to get around to, I hope people are still interested in catching the end (or is it, season 6 and all) but I really couldn't think of what to put here. I hope it came off alright.
"This thing, with Sam."
There's no warning, just like the first time, just like every time, Castiel is just there. He's wearing the body of Jimmy Novak and Dean wonders what that man is feeling, or if he feels at all anymore. Castiel might have made him sleep, hidden him from the reality of their situation.
Whatever gets him to sleep at night – that's what he'll believe.
"Letting him walk Lucifer back into his prison?" Dean takes another shot of whiskey, tomorrow they end the world or save it, their pretty much dead in any case.
"You know it's not going to work." Castiel says softly, sitting beside him. "There's almost no chance that it'll work."
"Great pep talk."
"If it does..." Castiel continues, stiffly, like he's practiced this, thought about it. "If Lucifer goes back into the pit, Sam with him...find somewhere, anywhere to go, and forget about hunting."
"No. Sam told me about a woman...Lisa? You should go to her. Be normal." His voice is lazy, like he's hypnotised himself into believing this. He gets up and goes to investigate the bottle on the table, pouring himself a glass and drinking it down with the ease of long centuries of practice.
"And if I want you? If I live and you live and I want you?"
"A demon, in the body of an innocent man, with a family no less...a demon who lied to you, who'd screw over your brother, sacrifice everyone you've lost over again, hell even your parents if they were still around, if it meant I got to live, and I got to keep you." Castiel's voice is monotone and pointed. "You're right, lets buy a house...we'll steal a child together, one that looks like me."
"I'm serious." Dean restrains himself but feels anger filling him anyway. "Where are you going to go? When it ends?"
"Presuming Lucifer hasn't either gored me, or won out?" Castiel is quiet, sombre. "I have no idea." He holds Dean's eye, his tone strengthening. "But there is no future in this, Dean. Know that, before anything else happens. We end with Lucifer."
"I'll still want you."
"That doesn't mean I'm good for you." Castiel speaks with a finality that renders Dean incapable of arguing. Instead he gathers all his strength, every conviction he ever had and all the things that were worth fighting for, the few that still are, and he crosses the space between himself and a demon, ready to lose himself one last time.
They are both adamant, internally, even as they move together, even as Castiel spreads beneath him for only the second time since they've known each other, they are both certain that what they feel is not love.
They are both wrong.
They lose Sam to Lucifer, they lose everything to Lucifer and Dean drives into an almost empty graveyard with his Father's car and his Father's music and not much more besides an empty seat where Castiel should be.
He stands in front of the devil, the fallen angel wearing his brother's face. He stares at Michael, who was meant to steal his freewill, and settled for enslaving his half brother.
Dean realises he hasn't got a hope in hell.
Fire hits Michael, sending him away in a flurry of screams and flames and the stink of burning feathers. Castiel watches from his place by the car that drew up without Dean noticing. His arm is still held out, caught in the act of throwing.
"Castiel" Sam's voice. Lucifer's voice. "You've forgotten yourself." It means so many things, he's forgotten the devil who made him, forgotten his job, his species, his purpose. He's forgotten that before he was a demon he was a man, and a terrible one at that.
Lucifer snaps his fingers and Jimmy Novak splits open like a rotten fruit, spilling his mortal remains.
Black smoke screams towards the sky, and with a wave of his brother's hand it is incinerated.
Dean stands in front of the devil, and talks. Because it's all he has left to do.
Later, kneeling on the ground that sucked his brother and two angels down to hell, his face a beaten mess of blood and bruises, he'll wonder why it worked.
"Dean?" Castiel is standing over him, housed safely in Jimmy Novak's sullen meat.
"Cas?" his mouth hurts, everything hurts, but the demon crouches down, laying a hand on his shoulder.
"It's ok." A soft hand in his hair and he's being helped to his feet, resting against a smaller frame that might as well be steel for all that his weight seems to trouble the other man. "You need to go to a hospital."
"Sam...Sam is no longer within my reach." He helps Dean into back of the impala, lying him down and closing the door. "You're my only concern right now." Castiel sits at the wheel of the car, slowly starting the ignition and going through the process of changing gears. There is no music, no sound except for the grass and small stones beneath the wheels, fading to the rumble of road and the quick press of the wind against the windows as the car speeds up.
"Dean?" The demon looks up at the mirror, a frown of concern on his face as he checks on the man resting across the back seat.
"Don't leave." His voice is quiet, paper thin. "Don't leave me."
The silence is the most painful thing since watching his brother fall into hell, it puts his wounds to shame.
"I won't leave you." Castiel's voice is rough as usual, but cracked minutely, emotion showing through.
Dean allows himself to sleep then, or lose consciousness, he really has no idea. Only later will he come to wonder how Castiel is back. That for some reason a God no one believed in, a God no one could find, had brought a demon back to life, taking the soul of its host into heaven, and leaving a body for it to use.
Even later it will occur to him that they've won.
If you can call it winning.