One-shot inspired by a tumblr post by casfucker: "gadreel and crowley were inside sam. on a scale of 1 to 10, how pissed do you think lucifer is right now?" jeni-thunder replied "666?" and luciferissatan replied "very". It was a plot bunny I couldn't resist.

Season 9 and 11 spoilers. Set during Season 11 Episode 10 "The Devil in the Details." Dialogue taken from the show.

Lucifer nibbled his thumbnail, quelling the anticipation rising within him. He was eager to break Sam as he had done so many times before. Sam turned to him slowly, the reality of his situation finally sinking in. The tone of Sam's voice told the angel that he was loathe to believe it. "You? The visions... everything... it was all you?"

"Impressive, right?" It rather was, Lucifer thought pridefully.

"And Rowena?"

"Did as she was told. Groupies... they're always so eager." Humans, he thought snidely.

"So you did all of that just to... to what... jump my bones?"

I've done a lot more for a lot less! "Literally," he answered curtly, opting to leer at Sam in the way he knew unnerved the fragile boy.

"Well, you wasted your time then. You see, I know how this ends."

Always so arrogant. "Oh, do you now?" He pushed himself off the bars and Sam backed away instinctively, leading them to circle each other.

"Yeah. You'll taunt me and you'll, uh, torture me, and I'll say no. And eventually, sooner than you think, my brother's gonna walk through that door and kick your ass."

Lucifer couldn't help but laugh. "Dean?" Sam nodded slightly. "You're betting on Dean?"

"I always have."

"Hmm. Oh, Sam. You got me all wrong," he speculated out loud.

"Ha, I doubt that." The false bravado coming off Sam was immensely amusing but also a little irritating. Who was Sam trying to fool? They both knew he was completely at Lucifer's mercy—or lack thereof.

"Oh, no. I'm not here to torture ya." Sam's eyes squinted in distrust. "I mean I could." He approached his wayward vessel, relishing his instinctive recoil. It was pleasing that Sam still feared him after all these years. Well, he would be foolish not to. Lucifer's voice dropped to a half growl. "I could inflict pain like you can't even imagine. I could inflict such delicious, perfect pain." And he could. The last six hundred or so years had given him plenty of time to plot his course of action when he once again encountered his true vessel. He knew the Winchesters would come crawling to him for help at some point. And at the rate they started world-ending catastrophes, it was going to be sooner rather than later. They were too smart not to use Lucifer as a resource, but they underestimated him. He'd made that error once when it came to the brothers and it was one he would not repeat. Now he had his chance. Releasing the Darkness was a bigger mistake than even he had envisioned, but it was a better situation than he could have planned. Only he hadn't expected Sam to brashly saunter in. Dean would go to any length to protect his cursed little brother. Which meant Dean didn't know. Oh, Sam. So devious. I guess you haven't changed much...

He returned his attention to the shaking figure in front of him. Unadulterated fear was radiating off the man and Lucifer savored it. His dilated pupils, his quivering jaw, the compulsive swallowing. Everything in his body was fighting against the scream building in his soul. "But that was so five years ago," he added lightheartedly. Sam looked confused. "No. I'm not going to harm a glorious little hair on that glorious little head."

Torture would not be his primary tactic. Both brothers had endured decades of it. Sam had suffered for 180 years under Lucifer's sadism. Nothing he did now would convince the pathetic human to say 'yes.' Instead he decided to play upon Sam's sense of honor and duty. Given the right pressure, Sam could be made to do anything. Ruby's manipulation was evidence enough of that. But here, Sam really would be saving the world from the Darkness by saying 'yes.' Surely he would see that?

"Then what do you want?"

"To make an offer you can't refuse. You see Sam, you need me," he shrugged to convey the futility of resistance, "and I'm gonna prove it to you."

He raised his hand to Sam's forehead, ready to push inside Sam's mind and search for the memories he needed. Sam closed his eyes and immediately surrendered, which surprised Lucifer, who had expected a violent resistance. Something was different. Why wasn't Sam fighting? Sam had won the last time they'd mentally dueled. What had changed? He touched Sam's consciousness and felt himself rejected. But not by Sam. Confounded, he pressed harder but was again rebuffed. He didn't recognize the force repelling him. He drew on his grace to pierce the human's psyche and the resulting metaphysical pyrotechnics gave him the clue he needed. Grace. The tiniest trace of grace within Sam, defending him, protecting the vessel.

Angelic grace. And it wasn't his.

Anger flared in Lucifer. Another angel had dared take Sam Winchester, his true vessel, as its own?! Lucifer retracted from Sam's mind momentarily, shocked by the unexpected discovery. He returned to his previous entry point into Sam's damaged mind and gently pushed into it. The grace slashed at his consciousness and he focused on it. Who would dare insult Lucifer and take his vessel? He touched the elusive wisp curling before him and was appalled by its owner. Gadreel?! The sentry who let Lucifer into the Garden. How had Gadreel even gotten the chance to possess Sam? Last he knew, Gadreel was locked up in Heaven's prisons when Lucifer was cast down. Had Gadreel been set free? While he had been left to rot in the cage? The injustice of that thought threatened to consume him so he returned to his present engagement.

Lucifer began to sift through Sam's memories since he had returned topside. He was gratified to see how much Sam had suffered from his memories of the cage; he expected his own residual grace entwined with Sam's soul would have had this kind of catastrophic impact on the man's fragile psyche. However, he was also slightly dismayed, for had Sam killed himself and his soul been cast into the Empty, he might be out of a true vessel for quite some time. He found it irritated him that Dean seemed so dismissive of Sam's suffering. Lucifer had broken Sam countless times. Did Dean underestimate his abilities? Or was Dean just that stupid?

Flashes of purgatory and trials to close the gates of Hell rushed before him and he realized he had again underestimated the brothers. Not only had he almost lost his vessel, he could have been trapped in Hell forever. This was unacceptable. He had to get out. He had to.

Returning to Sam's mind, he stood as an unnoticed observer as the angels fell, explaining how Gadreel was freed from Heaven. He watched as Dean manipulated Sam into saying 'yes' to Gadreel. He seethed with rage as Gadreel slowly infiltrated Sam's soul. Gadreel knew, he knew this was Lucifer's true vessel, and yet he had the gall to take from the Morning Star!

Suddenly, as if Lucifer's outrage called to Sam's, a surge of indignity from his vessel's psyche enveloped him. How dare Dean do this to Sam?! After Dean, autonomy was what mattered most to Sam. Being able to make his own decisions. It's what had driven Sam away from his father, what had bothered him the most about Azazel's blood pulsing through his veins, what was the worst insult of the loss of his soul, what constituted the worst torture while in Hell. Lack of control was anathema to Sam. How could Dean betray Sam like this? To trick his brother into saying 'yes' to an angel, again, after his soul had been ravaged by one already. As if hosting Lucifer hadn't been a crushing enough experience, Dean just had to shove another angel into the crumbling body of his little brother. And for what, so he wouldn't be alone? How selfish! Lucifer burned with fury, a flash of sympathy rising in him as he recognized Sam had been abused by his big brother for his own needs, just as Michael had done to him. Lucifer struggled to regain control of his emotions, the cruelty of the situation readily apparent, not to mention that this would make his strategy all the more difficult to enact.

A whiff of sulfur caught his attention, breaking him from his reverie. A demon? … Not just any demon… Crowley. The usurper. Crowley had possessed Sam too? Peering into Sam's memory, he saw what had been done. Dean and Castiel had allowed Crowley to possess Sam to push out Gadreel. This was too much. Crowley would pay dearly for polluting his vessel. Only Lucifer had the right to tarnish it! And Castiel – had he no sense of honor, of dignity? And here Lucifer thought Castiel loved humans. But to allow one to be the playground of an angel and a demon simultaneously?! Lucifer roiled with disgust. He retained no great love for Sam Winchester after the man had betrayed him, but he resented the disrespect the others clearly held for Lucifer. If they truly feared him, they would never have engaged in such egregious affronts to Lucifer's power. They would all pay with their lives for their miscalculation.

He sighed and suppressed his righteous anger as he had done so many times before and focused on the task at hand. Wills to bend, vessels to inhabit, prisons to escape.

And this time, he was staying out.