He was rarely sober these days. Drugs helped him to pretend he was happy, and absinthe clouded his mind enough to forget, just for a few hours, how distant Dean grew from him. This was no longer the Dean he knew, this was a stranger who despised him - probably rightfully - and never realized it was his coldness that pushed Castiel on this path.
His Dean would have cared. His Dean would have yelled his head off and beaten him up to drag him out of this, but the soldier was long past caring. At first, Cas tried drugs out of curiosity, then out of despair. Everything went wrong, long before Sam gave in to Lucifer. That was just the last straw. He played the merry hippie and fucked anyone who was willing, but everything he did was a cry for help. In the beginning he hoped Dean would understand it. But by now he knew something broke between them and couldn't be fixed. Now he only kept up with it because drugs gave him wonderful visions - visions where Dean was still his old self, Sam was the kind and loving friend and Cas was innocent and naive. Oh, how he wished for the blissful ignorance. The times before he found out his own brothers were traitors, and Father didn't give a fuck anymore. That was when he first broke down.
The worst part was that he still loved Dean.
Every night, after the girls fell asleep and the effect of drugs began to wear off, he took out his sword, watching silently as the moonlight danced on the blade. But he couldn't do it. Dean needed him, even if he wouldn't admit it.
Meeting the past Dean was the most painful thing. Cas joked and laughed but all he wanted was to grab him and go back with him in time - if only he still had his powers. But he knew Dean would not want him. Not this disgracedhim.
There was no point in going to meet Lucifer, they never stood a chance. But Dean wanted to go and he followed. He always followed.
He expected to be killed quickly - he was nothing but human by now, any weapon would work on him. But the bullets avoided him. Later he found out it was on Lucifer's commands.
He was knocked out during the battle. By the time he woke up, it was all over. Sam - no, Lucifer - waited for him in his rose garden, all in white. He looked so innocent and sweet, yet there was something deeply wrong with his appearance. Those eyes made Castiel shiver. Dean was dead. Of course he was dead. He was no match for the devil. And past Dean was gone.
"Long time no see, brother" Lucifer purred, not even looking at him. He was more interested in the perfect rose in his hand. "By the way, the sword won't work on me. Others have already tried. Tell me, how does it feel? Are you sad? Angry?"
Castiel was past feelings. He was just tired.
"Kill me" he said. "I didn't come here to listen to your gloating."
Lucifer finally turned around to face him. Why did he have to look so much like Sam? Why?
"Why would I kill you? You are no more threat to me than a kitten. Look at yourself... useless, powerless, fallen. All because you loved your precious human who didn't even care."
Castiel didn't answer.
"Do you know Sam is still inside me? Oh, he's heartbroken. He was screaming at me to stop. I could never make him learn loving your brothers only brought you pain."
"You are not even worthy to say his name, you son of a bitch."
"Do you think you can piss me off enough to smite you? Oh, Cas. Letting you live is much more fun. Go, give your boyfriend a nice funeral. By the way, more and more of our brothers come crawling to me and beg me to let them join my cause. Michael stands no chance. Oh, he could resurrect Dean, of course, but he has given up on this stupid ape long ago. Did you know he resurrected John Winchester last month and he was declined? Like father, like son. I had much easier with Sammy here. The poor fool. He actually believed I would spare his brother. But I keep one part of my promise. I spare you."
And with that, Lucifer vanished.
Cas took Dean's body in his arms. He wanted to say that he was sorry, that he failed him, but there was nothing left to say and Dean couldn't hear it anyway. All he could do was what Lucifer said - give him a nice funeral.
Only him and Chuck stood beside the pyre that night.
"You have written this already" he said.
"All of it" Chuck sighed. "Cas, is there anything-"
"No. And you know that."
He want back to his house and found the girls there, waiting, but when they saw his face they fled without a word.
Cas took a much-needed bath to get rid of all the blood. He even shaved properly, then got his old suit and trench coat from the bottom of his wardrobe. They were torn and blood-stained, but putting them on felt like going home. He walked out into the starless night, finally stopping by the abandoned Impala. He reached out to caress her and suddenly he broke down in tears, falling on his knees and nesting close to the dead car.
"You know he loved you" he sobbed. "But he couldn't fix you anymore. I knew you were always watching him. You thought he abandoned you... and it hurt. And now he's gone. I would take you for a last drive, but I doubt I could make you work. I'm sorry, I'm so sorry. In a few years, your boys will be forgotten. Humanity will be forgotten. But you will remember." He tried to smile. "Farewell, old girl" he whispered. Then he drew Dean's gun from his pocket. He didn't need the sword - he was not worthy to die like an angel. He sighed, closed his eyes and raised the gun to his head.
Chuck was not surprised when he heard the shot, after all, he had seen this coming. He found Cas by the car, in a pool of blood, his wings burned into the ground. Mayhaps in the end, a little bit of grace was still left in him.