1. Release
Cas came for Sam almost immediately after he, the Devil, his brother, and Michael landed in a heap on the floor of the Cage. He had an angel blade in his grip and spoke with authority that Sam had never heard come from him before, "I'm taking Sam and Adam."
"No you're not." Lucifer glared at Castiel, his hand gripping Sam's arm tightly. "Or maybe you'll take Adam, but I'm supposed to keep Sam."
"You're wrong. You were supposed to take his body and burn up his soul so he could go to his eternal reward in Heaven for following the will of God," Cas corrected without even blinking.
Sam's mind was frozen – I get a place in Heaven? – and his body was numb. Adam had already crossed the floor to stand next to Castiel (well, cower behind Castiel was more like it). Michael stood up and asked with a quavering voice, "What about me, brother?"
Cas bowed his head, but said nothing.
"You mean our father doesn't want me to come home?" Michael was crying, taking a few steps forward, "I've been the most loyal son any father could ask for, and he said to leave me here?"
"No Michael," the reply was almost missed it was so quiet. "We decided to leave you here, because our father left us without any commands whatsoever and you betrayed us. You made us follow your will and made it seem like our father never left. We see that now, and we decided you will be punished for it." Cas looked up, his face stormy and unforgiving. "We condemn you to the punishment you always set for angels who chose free will, because while you exercised yours, you denied us of our own."
"I only did what I thought our Father would have wanted," Michael pleaded.
"Based on the events that led you here, I would say you thought wrong."
The so-called loyal son didn't say anything, just cast one last teary, hopeful look around the prison. Finding no sympathy, he looked down and sighed, "Well if you have the power to choose, then so do I," then snapped his fingers and exploded in a burst of light, leaving only scorch marks on the ground.
When the brightness diminished, Cas extended his hand to Sam, who was still frozen in place. "Are you coming, friend?" The question was asked gently, but he looked at Lucifer with malice and threats in his eyes, and the Devil let go of Sam's arm that he'd been holding. Finally processing all of it – He's letting me go, Lucifer is letting me go and I get to go to Heaven! – Sam ran to Cas's side as if he'd been burned.
Cas nodded, one hand holding each Winchester brother, and they walked out of the Cage. But just as the door was about to close, Lucifer silently lunged forward and snatched Sam's soul from his body and pulled it back into the prison.
"I don't think anyone even noticed," he grinned evilly over the ball of light that was quickly settling into form as a duplicate of its former host body. "Now this is gonna hurt like a bitch, so try not to scream."
The Cage door slammed shut, and Sam's torture began.
AN: The idea of Cas getting Adam out with Sam's body was already done by cashasthebluebox in the fic "The Cursed Child", thank you for the inspiration!
Also, the bit about Sam not being allowed to scream is not mine but I've read a ton of fics that incorporated this that I don't know who to credit. If you know, message me!