Castiel stopped being God in the same place where he started: the old, deserted building where Raphael met her demise.
What Castiel had been doing in that place, Dean couldn't even begin to guess. He himself was only there for the rumors that Raphael's archangel blade could kill lesser gods and that said blade might have been hidden there somewhere. How he would use the blade on a creature that can explode an archangel with a snap of his fingers was beyond his imagination, but hey, he was nothing if not creative. He'd manage it somehow. Maybe. He didn't know. Either way, with Cas as powerful as he was, Dean preferred to take his plans one step at a time. No telling whether he would survive even a step of it, after all.
Turns out, he was right. Because the moment he picked up the archangel blade, he knew.
Dean couldn't explain it, because nowadays Cas barely made a sound when he flew, but in that moment, there was no doubt in his head that Castiel was standing right behind him. So Dean froze. Closed his eyes and opened them again, and let out an explosive sigh.
He was so fucking tired of this.
"Well?" he snapped. It was a stupid action, but he doesn't care at all. "Get on with it."
There was silence. And then, just when Dean started to think that he was imagining things, he spoke.
"Dean Winchester." Castiel said, because as a God Cas sure does love to be dramatic. "I have offered you mercy. And yet you have wasted it."
"Spare the speech, Cas." Dean snapped. "Do what you came here to do."
Silence, again. Dean imagined Cas doing that little confused head-tilt, and immediately wished he hadn't.
"...I warned you." Cas said. Dean probably imagined the reluctance in his tone. "I..."
And in that moment of inaction, Dean moved fast.
His feet slid apart, grounding himself on the cold hard floor, and Dean spun around. His hand—the one without the angel blade—grasped the angel's collar and yanked him forward and off-balance, while the one that wielded the angel blade swung back. With the sound of knife tearing flesh, the blade struck true. A direct hit to the heart. Quick. Efficient. Ruthless.
Dean didn't let go.
This was his last hope. There had been nothing—nothing—that had stopped Castiel's rampage, and if this didn't work...
Castiel's knees buckled, the body in Dean's hand suddenly growing heavier. The blade twisted in his hand, hot and slick with sweat but Dean still didn't let go, holding on with all he's worth. He owed Cas this, at least—he killed Cas, Cas, who saved him from hell, Cas who's not a hammer, Cas, who doubted, rebelled, and fell for him. Cas who risked exploding himself so Dean would not be dragged away from his happy, apple-pie life.
Cas, who broke Sam's wall and his very sanity as a distraction.
So Dean held him, and looked him in the fucking eye as those brilliant blue eyes, alight with hurt and betrayal, blinked slowly back. Let Castiel clutch at his shoulders and try to drag him down to the ground. He held him, made damn sure the sword didn't move 'cause he knew it would hurt as fuck if it did, and didn't look away even though there was nothing else in the world he wanted. He had to watch the death of his best (only?) friend, if only because he was the one who killed him in the first place.
It was stupid, because this creature (Cas) was probably not his friend anymore. It was quite probably the souls of purgatory, (Cas,) and here Dean was trying to make it (him!) comfortable in its last moments. Still, Dean made himself look. Still, he blinked away the tears that were blurring away his vision, looked at those clear blue eyes and pretended that he still had his friend there with him. Still he pretended to ignore the slow warmth seeping through his jeans, the steady dripdripdrip of blood to the floor, and the fact that there was a steadily-forming puddle of blood right there beneath his feet.
"Dean..."
The words came out as a pained gasp.
"Dean." The creature... Cas, croaked. "Close... your eyes..."
But he couldn't. Could he? Dean shook his head, blinking rapidly. Cas deserved this. Cas deserved to have someone with him when he died, even if that someone is a shitty excuse of a human being and an even shittier friend. So Dean kept his eyes fixed on Cas'. He wasn't sure he could close it anyway.
"Cas?" he said, voice hoarse with tears. "Castiel, are you—"
Cas' hand lifted itself from his left shoulder, almost bringing Dean to his knees as the pressure over his right shoulder doubled. The hand settled gently but firmly over Dean's eyes, cutting off his view of Cas' clear (sad, wide, innocent) blue eyes, and the angel (his angel) gasped out with his dying breath—
"Don't look."
just close your eyes
the sun is going down
you'll be alright
no one can hurt you now
come morning light
you and i'll b an d