Day followed after day. He barely noticed it. Time had lost all meaning in the moment Dean had turned around and had left him, not an angel, not a human, not even Cas anymore.

Sam counted every minute, every second bringing new agony of terror and ever-diminishing hope, and Cas hung around, trying to be there for him when he wasn't even sure he was there at all; maybe he had ceased to really exist looking at the blade stuck a few inches from his face, knowing that Dean could have plunged it into his body and he still wouldn't have tried to fight him.

Sam was frantic, adamant in his belief that his brother could be saved. Cas knew he couldn't. Dean had gone too far, had become lost.

And yet –

And yet there was still a part of him left. And that was what hurt the most; knowing that there was a small sliver of that soul, of that bright, wonderful soul that Cas had once rescued from Hell, left even as Dean was murdering and torturing innocents without a second thought.

Cas could not even wish that Dean had killed him. He didn't want him to be alone. He couldn't bring himself to leave him alone in a world he was set to destroy.

It took years to make the younger Winchester finally realize that going against his brother openly would lead to his demise; years of still warm bodies left in Dean's wake, years of news coverage of the serial killer that had died twice and yet come back again, years of research.

Cas never could really convince him to let go. Start a new life. As long as he kept away from Dean, nothing would happen. There was just enough left of Dean to prevent him attacking his brother without reason.

Sam stayed at the bunker, rebuilding the Men of Letters, and soon there was a constant coming and going of young and old hunters, even friendly monsters and witches.

Cas came and went a lot too. He came when Sam called, when he needed his help with a spell, research, or when it was one of the bad days when he remembered Dean sitting next to him, eating or laughing or complaining about the reading he had to do.

Cas always drove.

He still reserved flying for Dean.

He had to search for him now. Before, he would have prayed, or Cas would have felt longing. Longing. How well he remembered the pull, the pleasure at the realization that his friend wanted to see him.

There was no longing. Never again. Dean, who had walked away, Dean, who had threatened to kill him, Dean, who would have done better for him if he had used the angel blade, didn't long for his presence. Cas didn't know if he even remembered, or if the years of blood and anger had swept away him, Sam, the Impala.

He stayed young. Just like Cas, Dean had become immortal. He didn't know when; maybe when he had taken the Mark, maybe when he had turned into a demon; but Dean always looked the same, like he had when the blade was raised above Cas' heart.

Dean never knew he was there. If he had, he wouldn't have hesitated. He wouldn't have missed.

But Cas didn't reveal himself to him. He watched, like he had promised he would.

Not always. Even when he had nothing better to do, there were moments during which he couldn't bear to be in the same place as the once righteous man.

A young boy cuffed to a table, Dean taking his time separating his skin from his bones.

Cas didn't know what the family had done to deserve this fate. They had likely not done anything.

Dean was simply doing what he was supposed to. What the Mark told him to. What he needed to feel good, to feel in control.

The Dean he had known would have been terrified.

But that Dean was almost gone.

Well, that Dean was always kind of a dick.

The words came back to haunt him. He hadn't been "a dick". Or had he? Years of close friendship with humans had taught him many things, but the subtleties of their language had always been a mystery to him. Sam had often called Dean a dick. But usually there had been a fond look on his face when he had done so. It was all rather confusing.

He wished he could be as confused as to his feelings, like he had been when he had first met Dean Winchester. Feelings had been new then, doubt just beginning to gnaw at the beliefs he had held for millennia, and it had taken him long, too long, to realize that he loved the Winchester brothers, but not in the same way; and that the love he held for Dean was one that angels were not supposed to experience, was human and terrifying.

After he had realized, after he had looked at the hunter and known, he had never revealed it. Dean wouldn't have accepted it, and he didn't want him to lose a friend because of his feelings. Dean needed him as a best friend, an angel, a warrior. He didn't need, nor would he ever want him, as a lover.

Hadn't wanted him. Hadn't needed him. All that was long gone. Dean was long gone.

But Cas had stayed, spending eternity watching Dean destroy the world they had saved.

He was there when Sam died. Although he had never left the bunker or got married, Cas, remembering the last thirty years, assumed that he had been happy. The Men of Letters had grown in numbers, hunters everywhere on the planet were asking for the help, and there were many visitors for Sam Winchester on his death bed.

Cas was the last one, and the one Sam asked to stay.

He had lived a long life, even by non-hunter standards. He had spent more years without his brother than with him.

And yet Cas still saw the same loneliness in him that he had first seen on the day Dean left the bunker for the last time.

All those years Sam had been running the Men of Letters and hunting, but since Cas had told him, looking him in the eyes, finally getting through to him, that there was nothing they could do, that Dean was working towards the end of the world, his name had not fallen between them.

"Dean..." Sam began, his breathing laboured, and Cas thought that if it should be his last word on earth, it would be fitting.

He reached out and squeezed Sam's hand.

The last friend he had in this world.

He wished he could say he would be fine, lie as he had during the Apocalypse.

"He won't be alone" he vowed instead, and Sam feebly squeezed his hand back.

His last word wasn't Dean. His last words were Cas – thank you.

Sam went to Heaven.

Cas knew what he had seen there a long time ago.

He had no doubt that now, it would be full of memories of Dean.

After Sam had died, watching Dean was all he did. He had sworn that he wouldn't be alone. And he never would be again.

Dean was not a demon, but he wasn't human anymore either. He barely ate. He barely slept. When he needed to move, he stole a car, and Cas sat next to him, invisible in the passenger seat, and in the silence he remembered loud rock music and the smell of take out.

Time had lost all meaning that day in the bunker. Now it gained some back.

Time was anther scream ripped from a throat, then smothered in blood.

Time was bones breaking, a mother pleading to spare her child, that child torn apart in front of her.

Time was Death appearing to claim another victim, his eyes boring into Cas', both visible only to the two of them, two spectators as humanity was eradicated by the greatest hero it had ever had and never known.

Time was the failure of technology, of politics, of economy, earth turning into a waste land, Dean Winchester still wandering, an animal, a predator.

There were only a handful of humans left. The changed climate had made life for them almost impossible, and Dean had done what he could to destroy the rest.

And yet Cas stayed to see the end.

The last man on earth didn't put up a fight. He knew what was coming for him, knew that a monster was lurking in the shadows.

Long after the Winchester Gospels had fallen to dust, another legend about Dean Winchester had been born in pain and hatred, and it had accompanied humanity in its last centuries.

The man didn't scream as Dean killed him. Mankind ended with a whimper.

His watching days were over.

Cas became visible.

And looked into Dean Winchester's eyes for the first time since that day in the bunker, long ago vanished.

The green eyes that he still loved as fervently as he had when he had looked upon them, blazing with life and happiness, sitting with Dean on the hood of the Impala.

He had never asked what became of the car after Sam's death.

It didn't matter.

What mattered was to see Dean one last time.

He recognized him.

"Cas".

His voice was flat. He didn't ask why he was here, where he had been. He didn't care.

Cas stood still as he approached him and drew an angel blade out of his jacket.

He expected to die.

He didn't expect a kiss, painful, painful and real, pressed roughly against his lips, Dean's hand, dirty with the blood of millions, clawing into his trench coat.

He didn't know if it was another torture. If Dean knew, had always known, and was using that knowledge to taint his last moment on an earth he had watched being created and bear the most beautiful soul in all of creation only to have it be destroyed and take everything with it.

He didn't care if it was torture. All that he cared about was that Dean's lips were still moving against his as the blade was plunged into his chest.

Dean had given him this.

And he loved him for it as he died in a waste land, kissing what had once been his righteous man.