Chuck is eating some unidentifiable Chinese takeout and getting grease all over the maps. Lucifer (not Cas, and how had he ever been fooled for even a moment?) winks across the table, and Sam clenches his jaw to keep himself from swallowing. He’s positive Lucifer sees the aborted motion all the same, and suddenly he can’t bear another second in the war room with these two beings. He doesn’t even bother to make an excuse (wouldn’t fool Lucifer, Lucifer knows him better than anyone ever will), just stands abruptly and leaves.
The bunker is a vast subterranean network of libraries and storerooms, with halls and basements and locked rooms that even after years, Sam has not fully explored and catalogued. The bunker is too small. Sam snatches a book at random from the library table and retreats and retreats, follows hallways away from the library until he finds a dusty little room he’s visited only a few times.
Sam turns on the dim light, still active, fumbles closed the door, tests it. The room itself is tiny and spartan—might have been a student’s study space at some point in the Men of Letters’ heyday, just a wooden chair and a simple desk still covered in notes from the last time he worked here. He grasps the chair to pull it out and finds himself pushing it in front of the door before he knows what he’s doing.
It’s such a pointless, childish gesture that Sam is surprised at himself. It would hardly deter their houseguest, should he come looking, and Sam very nearly laughs. (Lucifer would definitely laugh. Always such an ego boost to see you work yourself up like that for me. You’re a real flatterer, Sam.)
He takes a breath. He forces himself to pull the chair back to the desk. He sits. He puts the book on the table. He opens it. He stares blankly at the pages. After a long minute, Sam realizes he hasn’t read a word. He flips the book closed and for the first time notices the title: Schofmann’s Treatise on the Faculties of the Arch Angels and Their Lesser Brethren, Vol. 6. He flinches against a sudden chill of ice up his spine, swallows roughly against his rising gorge, pushes the book away. No use in that as a distraction, then, and he is quite unable to contemplate returning to the library.
Instead, Sam glances through his old notes as the icy, metallic taste of panic subsides. These are more suitable—no archangels here, just failure after failure in searching for an answer to the Darkness. The only answer is sitting in the war room, right now. The great evil Sam locked away, the one thing in all his life he knows he did right, undone. God wrote an epilogue about that, apparently.
So now here’s Sam, whose whole life amounts to what, exactly? Chuck had scolded Sam like a child for releasing Lucifer, but now he’s healed the guy from whatever Amara did, is talking family and strategy and who knows what else. Sam’s been trusting God all these years, and it turns out God doesn’t—God is—
Never mind that Castiel, another of God’s children, said yes. Never mind that Sam didn’t want Lucifer released again, never mind that he can taste Lucifer’s grace clinging to him like the stench of burnt rubber, body and soul and mind. (You're mine, Sam. Body and soul and mind.)
It doesn’t matter. Sam was the reason for the could-have-been Apocalypse. And yes, it stings that Chuck had written his ending and hadn’t lifted a finger to stop the fight between his warring sons, even when his created people was at stake. Sam has fought Chuck’s wars—between his various children, now against his sister. But this was childish, he knew, sitting in the dim study, feeling petulant that God favors one of his own sons over a perennial sinner too dull and desperate to learn from his own mistakes. Sam paid, Sam tried to pay, but— Sam always thought God valued faith.
Lucifer has faith, too, Sam knows him well enough to understand that. (And where did your faith get you, hmm, Sam? Same bunk as me.)
Prayer. Prayer was—it didn’t make things better, exactly, but it never made them worse. Even in the Cage it had been a kind of comfort, like screaming or begging had been a comfort, a release. Lucifer knew that too. (If you can keep silent during this next bit, Sam, I’ll let you be—lets say, for a whole day.)
Lucifer knew everything about Sam. Before the Darkness, before the second time the Cage was breached (no, too passive, the second time Sam breached the Cage) that fact was low on the list of Sam’s priorities. Because Lucifer was gone, not dead, and Sam had sometimes wasted time pointlessly wishing he was, but gone and locked far away.
Lucifer wasn't gone. Lucifer was in their car, he was carried on Sam’s shoulder, he’s in their home, and he is an essential weapon against the worst existential threat the universe has faced since its inception.
He’s lost time again, his hands resting numbly on the notes. He's cold. His head hurts. Sam rubs his burning eyes and glances at his watch—just past three in the morning—and then remembers that Lucifer has chosen a room, and the nausea he’d manage to push down earlier is back so suddenly he nearly doesn’t make it to the metal trashcan by the desk. But Sam doesn’t throw up, just gags emptily, shivers, and stares at the crumpled notes in the trash. Failed sigils, dead ends, meaningless rites, spells that don’t hold a candle to the power of the Devil or his relatives. As soon as Sam had managed to banish Lucifer (and Cas), he’d replicated the symbol Dean saw in that submarine as many times as he could. Warding like that is difficult to reverse-engineer. Sam considers himself a fair hand at that kind of spellwork, skill born of necessity, but the only real evidence he had that his improvised activation ritual took correctly was simply that Lucifer never reappeared inside the bunker to finish taking Sam apart. Of course, now he’s inside. So.
He's shuddering, still kneeling as if in some parody of prayer. He feels panic rising in his chest again, prickling up behind his eyes, and he doesn’t know if he should leave or stay, if this freshly warded room would be enough if Lucifer came looking for him, if Lucifer wanted to talk.
Having God in the same house must afford him some kind of protection, even if Lucifer doesn't exactly need much to hurt Sam. Sam's faith must extend that far, at least. Should he seek out Chuck, hide behind his stolen robe like some cringing child afraid of the dark? Then again, God himself designed Sam as a custom-built vessel. Lucifer’s been talking with Chuck for awhile now. Lucifer, God’s own son, and Sam knows better than most the extent of the crimes that family will forgive.
That conversation with his father must have frustrated him, he hates his family, Sam finds himself thinking with faint horror, and just like that his mind is running along familiar tracks, worn deep. Frustrated, he gets frustrated after he talks to Michael. Beg now, apologize now. No use hiding, no use waiting, it will only get worse.
Sam digs his thumb into the old scar hard to break the chain of thought. And there he is, shaking, tears on his face, alone in the dimness, his heart beating fast for no reason whatsoever, not even a hallucination or a nightmare to take the blame.