The battle was over quickly.
The definition of "quick" varies. The people of Earth, or what was left of them, were grateful when the battle ended after ten long years. Heaven's angels, on the other hand, rejoiced for such a quick and easy victory. Michael pulled Lucifer out of Sam Winchester and hurled him back into Hell, leaving Lucifer's vessel crumpled on the ground.
Michael in Dean's body made a speech to the few remaining people of Earth, telling them how now that he had won, there would be paradise on Earth. As had been promised for the past decade, as Michael exited Dean's body, the world changed. The colors became brighter; the birds began to sing. All of a sudden, the entire world resembled the Disney version of Snow White.
And Dean Winchester was left standing on a stage as the world transformed into Eden. He blinked his eyes for the first time in a decade, swinging his arms back and forth, trying to get used to being in control of his own body again.
Then he blinked again as he remembered what he had been thinking about for the past ten years: not the angels, not the war, just one thing: his brother—Sam.
He stumbled down off the stage and raced on wobbly legs to the thankfully close spot where he—where Michael—had left Sam.
Sam didn't understand. How could this have happened to him? He had trained his whole life to be the general, been completely faithful and had always risen to the top, beaten everyone else and every odd.
"You were never meant to win," a gravelly voice said from beside him. Sam turned his head to see a dark-haired man in a dirty trenchcoat looking down at him with pitying blue eyes.
"What?" Sam spat.
"Michael was always the foretold victor," the man told him. "You were never meant to win. I am…sorry."
Just as Sam opened his mouth to respond, venom in his eyes, Dean crashed into the clearing. "Sam!"
"You," Sam hissed, giving his older brother such a look of pure hatred that it stopped him in his tracks, making it clear with just one word that the moment where they had understood each other was over, and could never happen again. Would never happen again.
"Dean," Castiel said. "It is good to see you."
"Yeah, Cas, you too," Dean said. He didn't remove his eyes from his little brother. "What's…?"
Castiel walked over to Dean, put his hand on his shoulder, and gently steered him a little ways out of Sam's hearing.
"Cas, what are we going to do?" Dean asked, his voice sounding hollow. He kept glancing over his shoulder at Sam, who was still glaring at them, but apparently unable to move.
"There are…only two options," Castiel replied. "Your brother as he currently is cannot survive in Eden. He is full of hate, an unchanging hate that cannot be changed no matter how the rest of the world does. He has been under the influence of Lucifer since he was five years old, Dean. That is a long time."
"Yeah, Cas, I know all that," Dean snapped. He still hated to be reminded of that, still believed it to be all his own fault. "So what are the options?"
"We could kill him," Castiel said bluntly. Upon seeing Dean's face pale, he added, "Or I could regress him back to when he was six years old. The last moment before he was corrupted. Body and mind. Now, I realize this is not ideal, but I believe that you may find it preferable to his death."
Before Castiel finished his option, Dean had his choice already made. A chance to have his brother back, to be able to fix the mess that he had caused, to be able to take care of his baby brother the way an older brother should, the way he always had before…
"Do it," he said. Cas nodded, not looking surprised, and went back to where Sam still lay crumpled on the ground, Dean right behind him. Sam raised his head to glare at them as they approached.
"This will not hurt," Castiel said as he placed two fingers on Sam's forehead. To Dean, he said, "Shield your eyes."
Dean closed his eyes. There was a blinding flash of light, and then when it had faded away, he heard soft sobbing and opened them quickly.
Castiel was gone, and where the adult Sam Winchester had been was a small boy, just six years old. His eyes were squeezed shut, and he was sobbing. Hardly daring to believe it, Dean bent down and placed a gentle hand on his arm. "Sammy?"
"Dean!" Sam gasped, sitting up. He stared at his brother like it had been decades since they'd last seen each other. "You, you got old—Dean!" He wrapped his arms around his brother's neck and buried his face in his shoulder, crying even harder. Dean patted his back awkwardly. It had been years since he'd had to take care of a child.
"It's okay, Sammy," he said. "I'm here."
"I knew you'd come for me, Dean," Sam said, his voice muffled by his brother's jacket. "I knew you'd come and get me."
Dean rocked his little brother back and forth, and as tears started falling from his own eyes, he said, "I'll always come and get you."