Time was arbitrary in the cage. There was very little to measure the passing of time with. Once Death took Sam's soul, Adam was left to bear the full force of Michael's righteous rage, and it eventually proved too much. His soul and Michael's grace collided one too many times, until they collapsed into each other like a supernova. Lucifer was left alone, just like before; abandoned to wait for oblivion. Sometimes he would sense disturbances in Hell; he noticed the power struggle when Abaddon turned up, but that was nothing to the seizing of his tainted grace when the Darkness was released. He beat himself against the walls of the cage, his howls ringing across the void of hell. The Darkness wrapped his grace in razor coils and pulled, tugging and twisting and corrupting, until he could no longer tell which thoughts were truly his. All he can remember now is a terrible burning jealousy of the humans, of the creatures his Father loved more than He would ever love Lucifer. The Darkness would solve that problem, but it would also destroy his Father's true perfect creation, destroy the whole beautiful cosmos. That was something Lucifer could not, would not allow. He sent Hell shaking with the force of his rage, his desperation to escape. He hadn't felt that desperation in a very long time.

Desperation was a good motivator, but it wasn't enough to break a custom-built prison. Lucifer's grace folded in upon itself, curling inwards in search of a new answer. He couldn't help, couldn't fight, but maybe an appeal to the filthy humans and their selfish self-preservation would be enough. When he was topside, he could step into the dreams of any human he chose. This would require more finesse. The human who took on the mark would be the ideal candidate, but that human was more stupid than the rest. He cast around for something, anything, some spider-web thread of a link. Something in the very periphery of his consciousness vibrated, revealing a moment of weakness, of connection.

Sam.

His hope and his downfall, his escape and his return, his vessel and his betrayal. The human who had been strong enough to overcome the devil through sheer force of will, who had survived millennia of torture at the hands of archangels. The human who was supposed to be his counterpart, but turned out to be so much more. Lucifer tested the thread, projected his grace along it, gentle as he knew how, lest it snap. The thread trembled, and Lucifer steadied, but he wasn't causing the vibrations.

Sam was praying. Not to him, certainly, but it would do. Lucifer reached out, pushing into Sam's mind, and recoiled. Sam, his perfect vessel, was infected, tainted, by the Darkness. Lucifer howled against the awful taste of it, struggling to return to the cage, but he felt Sam shudder and seize as he heard the hollow shriek of Lucifer's voice, saw Sam's memory of the cage. The chains and the fire and the branding. The connection wobbled dangerously, and Lucifer withdrew, holding it still and praying himself that it wouldn't break. It stretched and strained, but held, and Lucifer curled downwards. He would just have to try again, and pray that Sam was strong enough to overcome the Darkness too.

Lucifer waited for what was probably years. The single strand of silk connecting him to Sam's mind occupied his full attention, everything else pushed away. He kept a strand of his grace pressed against it, waiting for a vibration, for something that would let him reach out. He didn't dare push forward now; no matter how much he wanted to, the chance of the thread breaking was too high.

It felt strange to have a purpose again. He had been alone and adrift for so long that he had almost grown accustomed to the meaningless haze. He was still waiting, but now he had something to wait for.

Lucifer had expected the vibration to come from prayer, from Sam pleading with his father (although not even Lucifer could work out what Sam thought that would achieve). It came from something very different. It was only the slightest twitch, a flash of Sam's subconscious, but Lucifer was desperate enough to make it work. He traced the thread through to Sam's mind, and found himself listening to Sam talking about wanting to settle down. Lucifer couldn't work out what had triggered the connection; Sam's mind was as far as possible from hunting, from God, from any of it. He was talking about a domestic life. About wanting to be loved.

Oh.

Sam must remember the cage. He must remember Lucifer's refusal to let Michael touch him, must remember the possessiveness Lucifer felt. Lucifer had all but forgotten that himself, but even this brush with Sam's consciousness was stirring memories of the cage, of the apocalypse. Of the human who had been strong enough and righteous enough to fight against an archangel and win. Technically, Lucifer couldn't feel, but he did; something akin to fondness crept through him. He couldn't talk to Sam, not while he was awake, but waiting didn't seem like such a chore.

Lucifer made his move when Sam had been asleep for a few hours. He stepped into his mind, his grace straining to maintain the link. Dreamwalking was effortless when he was on Earth, but now, it was so exhausting it burned. He couldn't take the form of his old vessel, but he couldn't take someone too familiar either. This was a warning, after all. He settled on John Winchester, finding some amusement in taking the form of one of Michael's vessels. He let Sam pick the song that was playing, plucking it from his subconscious.

A good word to say

Guess it's 'cause he's just as wild

in the younger days

so blow you old blue northern

blow my love to me

It seemed fitting, somehow. He tapped his thumbs against the steering wheel.

"What are you listening to?" Sam asked, voice thick with yawning.

"Your mom used to love this song."

"Dad?" Sam asked. Lucifer turned to face him.

"You okay, pal?" Lucifer asked. He allowed his eyes to flick over Sam's body. "You look a little spooked." He looked down again, longer this time, noting the changes.

Someday soon, going with him someday soon.

Lucifer smiled as he turned off the tape.

"It's nice to be back behind the wheel," he said. "Looks like Dean's been taking good care of this old beast." He looked at Sam, and smiled. "Seems like he's taken good care of you, too."

"What is this? Another vision?"

"Are you having visions, son?" Lucifer asked. Maybe there had been more than the one he had triggered. Maybe someone other than him was trying to warn Sam.

"Don't call me that."

"What?" Lucifer asked. He'd always believed in playing his role, after all. "A father can't call his—"

"No, my father is dead."

Lucifer almost wanted to laugh. "When has death ever stopped a Winchester?"

"Look, I don't know what this is, but—"

"What you said about relationships, wanting something more," Lucifer said, interrupting. Sam couldn't be too resistant. He needed to hear something agreeable, "I never wanted this for you boys. This life. Not really."

"We turned out okay," Sam said, and Lucifer was surprised. He knew a thing or two about shitty fathers, and here was Sam, defending his.

"You did, didn't you?" Lucifer smiled. "But that was on you boys. You did that, not me."

"Well, you played your part." Sam said, and Lucifer had to control his reaction, fight back the smirk.

"I did my best, anyway, for what it was worth."

"This isn't real," Sam said. Lucifer smiled.

"I never could fool you, could I?" Lucifer asked, remembering their first meeting, in a very different dream; Sam had figured out who he was so quickly, and ever since, Sam had been one step ahead.

"I prayed when I was in that church," Sam said. "And I saw… something. And now here you are, whoever you are. Whatever you are. What is this?"

"Dream, vision, call it what you want. The message is the same. The Darkness is coming. And only you boys can stop it."

"Okay, fine. How?" Sam asked. "We need help, not visions of dead people."

"God helps those who help themselves." Strictly speaking, God didn't help anyone, but Lucifer couldn't just give the game away. He would give what help he could, and hope it would be enough. Hope that Sam could be too brave and too strong for his species one more time, and carry the whole stinking lot of them through and out the other side.

"Who are you?" Sam asked. Lucifer almost wanted to tell him. Almost wanted to let the line snap, just so Sam could know who was truly on his side in this. Instead, he retreated, let Sam wake.

Back in the cage, Lucifer kept a tendril of grace resting against the link to Sam's mind. It didn't seem so fragile anymore