Here we go! This is going to be an adventure :) This is my first fic, and the first paragraph was something I wrote as an omegle prompt! Well, have fun :)
Castiel lay slumped on the ground by the front of the Impala, hand clutched against a long slash across his abdomen. He'd tried, so hard. More than anything, he had tried to save Dean. But not even he could escape what Dean had decided to follow. He didn't know, of course. Cas had been stealing pages from the journal, making sure Dean couldn't find what Cas knew he couldn't fight-what, of course Dean'd try to fight anyway. The creature Cas knew that without a doubt, Dean would die fighting. He had managed to kill the thing-but not without nearly killing himself. He groaned, adjusting his hand against the blood-soaked shirt and trenchcoat that were now plastered to his body. "D-Dean!" He mumbled hoarsely, barely making sound with what was intended as a yell. He cried with a bit more volume, "Dean!". His head fell back to the pavement, leaving him a broken shell, not quite a man, and perhaps not all angel, but with wings still scorched onto the pale, worn cement of the sidewalk.
It was at this moment that Dean, perhaps hearing his name, or perhaps driven by hunger or lust or divine intervention, stepped out the door of his motel room, body turned behind as he exchanged a parting word with Sam. His head turned back to front, a laugh slipping out of his lips. Then he saw him.
Cas lay where he had collapsed, a few steps from Dean's doorstep and hope. A trail of dark blood stained the pale cement, marking where Castiel had taken his last, staggering footsteps. Dean fell to the ground, a cry of "Cas!" escaping his lips. He shook the angel, begging him to hold on as his fingers sought out a pulse. He heard, somewhere in the distance, Sam running up behind him, but it didn't matter. Sam was a mile, a world, a universe away as Dean Winchester, hoping against hope, on his knees and begging for his best friends life, saw the scorched wings splayed onto the sidewalk. Castiel was gone.