A/N So...um...this is my first fanfiction so, be nice? No flames please. Enjoy and please review :)
Disclaimer: I don't own the boys, though I do play with them a lot.
In Castiel's opinion, there's nothing worse than losing Dean Winchester. He could be damned to Hell, never to feel his brother's presence again, and he would not complain as long as Dean Winchester lived. He rebelled against his brothers, against everything he's ever known, for Dean Winchester. Nothing is worse than losing him, not rotting in Hell, not being hunted by his brothers. Dean Winchester must be saved, even if it costs more than Castiel can handle.
This is why on that day, April 13th, 2012, Castiel broke. His Grace pulsing in pure, unbearable agony. He felt Dean's death as his own, felt the knife slice through the soft skin of Dean's chest and pierce his heart. He felt the last pulses of blood through Dean's body, heard his last thought as it passed his mind. Take care of Sammy. Dean's last thought, his dying wish, was for his brother's safety.
Before he registered his actions, before his commanders could see him, Castiel took flight. He soared pass the gates and broke through the In Between that separates Heaven and Earth. He reaches the site of Dean's death within moments. Sam is there, crouched over Dean's lifeless body.
Tears fall freely from his cheeks while he says in a broken sob, "Dean, we just saved the world, you can't die yet. Not yet."
He repeats this many times, over and over denying his brother's demise.
Castiel kneelt down, staring at Dean's unseeing face. The intense pain had faded from his Grace, leaving only a dull ache in its place. He ran a hand down Dean's face, whispering his apology, his promise to keep Sam safe.
"Castiel."
Sam's tired voice forces Castiel to look at him. His eyes haven't strayed from Dean's face, his arms still encircling Dean's body, but he spoke to Castiel.
"Yes, Sam." It wasn't much of a question; Castiel knew what plagued Sam's mind.
"Bring him back. Now." The determination in Sam's voice slightly scared Castiel.
"I cannot. I promised Dean I would keep you safe. You will be ok." Castiel voice conveyed emotion, sorrow and anger. It wasn't enough for Sam.
"I don't need to be taken care of. Bring him back or I will."
Castiel sighed, "I am sorry Sam. Truly I am. But I can't bring him back. You will find no demon to deal with, and no angel to answer your calls. This is the last of Dean you will see."
"Then what's the point of you?"
Castiel winced at Sam's biting tone, "I am sorry, Sam. I would have stopped this had I known it were to happen."
Sam looked up, about to insult Castiel, but instead shook his head, "There's no reason for you to be here. Leave, and don't come back."
Castiel nodded, "If that is what you wish, Sam Winchester." Sam stiffened at Castiel's formal tone and immediately regretted his words.
"Cas, I-" Castiel left before Sam could get his sentence out. He dropped his head, squeezing Dean closer in his arms.
"I'll find a way to get you back. I promise, even if it's the last thing I do."