A/N: Lucifer has Sam, but he's not wearing him, choosing to use other temporary vessels as long as he can. The Devil's grown attached to his vessel and wants to keep him, make him happy. Sam knows he can keep the people he loves safe if he stays with Lucifer, so really, what choice did he have?

Summary: Sam saves Castiel's life, but all the angel can think is that it was too high a price to pay.

Small Mercies

"I am sorry Castiel," Lucifer sounded sincere. Castiel did not close his eyes, would not look away. This was the path he had chosen, with the humans, with the Winchesters, and he would never regret it.

Fingers grasped Lucifer's jacket sleeve.

"No," softly spoken. "Not him."

Castiel's heart clenched as he laid his eyes upon Sam Winchester for the first time in months. The boy stood next to Lucifer, looking at him with nothing but pain in his eyes.

Lucifer's hand was stayed and he turned to look at the human. Everything in Cas screamed at Sam to run, to get away while he could. Because, because…

But Sam didn't look scared, only very sad, resigned.

"Please, not him." Sam was pleading with the Devil for Castiel's life and it humbled him like nothing before. "Please…"

Lucifer sighed, his eyes softening further.

"He means that much to you?" His voice was gentle, consoling. "As much as your brother?"

Dean was always at the forefront of what Sam did. And suddenly the reason that Dean kept managing to make it out of every impossible situation he found himself in over the past months was clear.

Another realization rocked Castiel to the core and made him remember Lucifer the way he had been before his fall. When he had been the most beautiful of them all.

He truly cared for Sam Winchester.

Sam shook his head, mist gathering in his eyes.

"As much, but in a different way." Sam met Lucifer's gaze. "Not him."

After a moment, Lucifer sighed and lowered his hand; turning it from a weapon to destroy his brethren, to a comfort meant to soothe a human. Lucifer laid his hand on Sam's cheek. Sam made no move to lean into or away from the touch and he didn't break eye contact, shoulders squared.

"…Alright."

Sam finally breathed shakily, relaxing even as tears slid down over the Devil's fingers.

"Like your brother and the older hunter, I will keep him safe through whatever may be." Lucifer looked into Sam's eyes intently, a promise then. And that struck Cas hard because despite propaganda on Earth and in Heaven over the millennia, Lucifer did not lie.

Sam finally closed him eyes a moment in abject relief and Lucifer turned back to face the other angel.

"You have Sam's protection, brother, which means you have mine as well. Do not meddle Castiel." Lucifer would keep his promise. Dean, Bobby, and Cas were allowed to do what they pleased, even hunt and interfere with the apocalyptic plans, but if they became a bother, Cas knew they would be locked away for the duration. Not harmed, because Lucifer had promised, but kept isolated which would be distinctly unpleasant.

With that final warning, Lucifer raised his hand again to send Castiel away; back to the only other two beings in all creation to be personally protected by the king of hell himself. Not counting Sam, of course.

"Wait." Sam's voice was thread and thin, but effective. Lucifer glanced at him sideways. No words were exchanged, but Castiel was sure they were communicating. Lucifer nodded and took a step back, smiling gently at Sam who in turn stepped closer to Castiel.

The angel's heart picked up and he felt an emotion that he immediately knew he was not fond of. The desperation and apology and grief in Sam, the boy with the demon blood who had become his friend, his brother, broke his heart.

Cas felt the insane urge to lunge for Sam and run, try one more time to save him from the destiny Castiel and his kind had assigned him. Through tears, Sam smiled at Cas and the angel couldn't help but ask in a voice he thought too unsteady to be his own.

"Why, Sam?"

The human only shook his head. It was an unnecessary question and they both knew it.

"Cas…I…tell them I'm sorry. That I never meant…I tried and I never meant to hurt any of you." Sam forced one last smile, the brilliant kind that Castiel had only observed in him in his time before they'd officially met, before Sam had known of his destiny, before his brother had been ripped away from him. Never ending tears coursed down his cheeks, but Sam smiled through it, his voice wavering only a bit.

"Tell him I love him."

Cas could say nothing, choked by all the words that wanted out at the same time. Lucifer stepped forward again, a soft touch on Sam's arm as he regarded his heavenly brother.

Castiel's eyes did not leave Sam's until the hazel became green and he was staring at a familiar dusty library in a familiar dusty house.

Question came from all directions, but Castiel could say nothing. He sat himself down on the hunter's couch and looked at his hands that were useless to even save one of the people who had become so precious to him.

For the first time since his creation, Castiel cried.