Summary: In the cage, Sam offers everything in exchange for Adam's continued well-being; Adam really wishes he wouldn't.
Lucifer and Michael have never raised a hand against Adam. Why would they, when the mere threat of it brings the one they truly wish to harm to his knees before them? There he is: Sam Winchester, the boy who saved the world. See how he crawls now. See how he begs, so weak, so pathetic.
The sight brings tears to Adam's eyes every time.
"Take me instead," Sam always says. "Please, I'm the one who wronged you. Do whatever you want with me, I won't fight. I'll do anything you ask, just leave Adam alone. Anything."
Adam would give anything to be able to block out those awful words and the screams that inevitably follow. But that would cheapen Sam's sacrifice.
Neither Lucifer nor Michael care about Adam. Not really. But Sam cares. Sam cares enough to kneel at their feet, to lick his blood from their fingertips, to take all the hate they have to give and then ask for more—just don't touch Adam, never touch Adam, pleasepleaseplease.
God. It makes Adam sick with horror, sick with grief. Sometimes he yells for the bastards to stop, to leave Sam alone, to go ahead and take him. Any torture has to be better than watching Sam break. He's ignored. Of course he's ignored. Though sometimes, if Sam is still cognizant enough to hear, Sam will look at him, will glance in his direction with a plea in his eyes, like Adam is breaking his heart. And that's not fair.
Sam is a selfish bastard. A selfish, selfless bastard.
"I never asked for this," Adam always whispers over the tattered remnants of a man the archangels leave behind when they lose interest.
If Sam has been left with the ability to speak, he'll whisper back, "You're my baby brother. It's my job to protect you."
And Adam will weep until he has no tears left to shed.
I recently came across the following "headcanon" while browsing through the Adam Milligan tag on tumblr:
Headcanon: In hell, Sam would beg for Lucifer and Michael to take him. Just torture him. As long as it would bring Adam a moment of peace. What he didn't know... was that Adam preferred the physical pain to watching Sam be hurt.
This matches up pretty well with my own headcanon, so I thought I would attempt to articulate how I imagine things might have gone down there in the cage. Hence, the ficlet. So my gratitude goes out to sciencedoesntknow for the inspiration.