The doorbell had been rung twice in quick succession while Chuck was in the shower. It was times like this he wished he could control his powers, like some sort of weird astral projection. But no. Visions came on him at random, usually at inconvenient times... Much like visitors.

He moved as quickly as he could, possibly endangering his life by tripping on the stairs—yet he managed to get to the front door without dying, and he opened it, out of breath with a "Sorry—"

And he closed it again immediately.

"Would you mind letting me in?"

Chuck twisted the lock, as if that would help him. "Um... Yes. I would mind, actually." He held his hands flat against the bumpy glass of the door. "I like not dying?"

"I'm not going to kill you... yet."

"Wow, that's uh... very reassuring." Chuck backed away from the door. "Really got me there." He reached for the nearest thing he could find—did he have an umbrella? No. Of course not. Rain boot. Yes, a great self-defense weapon. Floppy, and harmless.

"Listen, I know I'm fallen and you're a prophet but hear me out?"

It was strange to hear Lucifer's strange lilting tone in Castiel's rough voice. Chuck brandished his shoe as he raised his voice. "No way! Scram!" He couldn't disguise the nervous energy in his voice, but oh well. "I'm not gonna trust Satan—who do you think I am, some kinda... kinda... I don't... know where I'm going with this. Just leave! Please?"

Lucifer laughed, or something close to it. "Well, since you asked so nicely..."

There was a long beat of silence. In fact, it was less of a beat and more of a drum solo. Chuck even let his guard down a little bit, relaxing into a more comfortable pose.

Almost the very moment Chuck's arms dropped, Lucifer began hammering on the door. Twisting the knob, shaking the glass. (Wait, was it glass? Chuck wondered if maybe it was plastic...) The door actually creaked under the force of his blows. Chuck raised his boot in self-defense.

"Stay back, I'm armed!"

Lucifer snorted. "I'm sure you're a massive threat." The deadbolt lock turned on its own as he spoke, and before Chuck could fully react the door had burst open.

Chuck threw his boot at Lucifer—Castiel—Casifer's face, buying himself enough time to run up the stairs. Of course, out of shape as he was, he didn't make it very far before Lucifer caught him and pinned him down. Weirdly physical, for this particular angel. Cold hands, and surprisingly grimy at that. Chuck fought off the urge to suggest a shower and instead blubbered out something about him being unappetizing and flabby.

"I'm not going to eat you." Lucifer made the most baffled, forehead crinkling expression as he bound Chuck's wrists to the banister with Castiel's tie. "Honestly, you humans never fail to disturb me. Why would I care about your fat content?"

Chuck made a face. "You tackled me on a staircase, okay? I'm not thinking straight."

Lucifer sighed. He stood up and straightened his—Castiel's—coat, as if that would make him less gross-looking. "Listen... human." He steepled his fingers in front of his mouth, seemingly deep in thought as he stared Chuck down. "You know something. I know you know something—whatever the Winchesters are hiding from me, you must know... You're a prophet." His eyes almost seemed to glow as he spoke. "Not just a prophet, The Prophet."

"I'm not—" Chuck tugged at his bindings. "Dude, I'm not some all-seeing... goddamn... messiah or whatever!" He leaned against the narrow wooden bars of the banister. "I just see stuff happening, as it's happening or maybe a little after the fact or sometimes a little beforehand but I can't like, control it and I sure as heck can't see deep into the past or whatever. I'm not a magical sightseer." He frowned. "Not—sightseer is the wrong word, I just—"

Lucifer held his hand up. "Please stop talking."

Chuck pursed his lips. He made to apologize, but Lucifer made a cutting motion with his hand.

"No." Lucifer clasped his hands together over his stomach. "You, Prophet, are... a nuisance, in fact."

"How dare you—I'm a goddamn delight." Chuck tried to kick Lucifer's shin, but he missed. And immediately found a rough, cold hand at his throat. Not tight enough to restrict his air but still a sufficient threat. He drew his legs back, pulling his wrists fruitlessly.

With Castiel's face full of Lucifer's aura and cold anger right up close, Chuck found it hard to think straight. All of his instincts told him to hide but of course there was nowhere to go. Instead he squeaked out some half-formed word. Cleared his throat at Lucifer's bemused expression and muttered, "You—you can't kill me—"

"No?"

Chuck shook his head. "I'm a... a prophet. And you—" He turned his head away from Lucifer as much as he could, preferring to avoid eye contact. "You're an archangel—it's your duty to protect the prophets from danger so you can't harm me because that would mean that you'd have to protect me because you're the last... last surviving archangel... Right?"

"You..." Lucifer frowned. " What ?"

"You can't kill me because you'd have to smite yourself!"

Lucifer drew back, pulling his hand away—much to Chuck's relief.

"That is absolutely not how this works."

Chuck raised his eyebrows. "It might be!"

"No—" Lucifer rubbed his temples. "You know what, let's just... Let's just humor you, for a moment." He sat on the stairs beside Chuck, almost casually. "Let's say that... If I try to harm you I will have to harm myself due to some strange clause in the Heavens..." He paused. "And I must admit, considering my presence here is in part due to a loophole, that may be possible..."

Chuck crinkled his face up.

"Assuming that harming you would violate my archangelic duty to protect you, I would then be forced to battle with myself—no, you know what?" Lucifer held his hands up, strangely saint-like as he spoke. "I'm just going to tie you to a chair and wait for you to work yourself into telling me what I need to know. I mean, how long can you go sitting in your own human... disgustingness..." He reached for Chuck, to untie his hands from the stairs but not from themselves.

"What—" Chuck tried to squirm away, but even in a body that didn't belong to him Lucifer still held much more strength than an out-of-shape author. "Wait, no, I don't wanna—"

Lucifer raised his eyebrows. "Do I look like I care what you want?"

Chuck continued to squirm—he couldn't think of anything to say so instead he just made various discontented noises as Lucifer dragged him down the stairs by his bound wrists. Chuck let out a litany of curse words as he went. Not for the first time in his life, he wished the F-word was an actual curse that could protect him.

...

Being tied to a chair was not particularly enjoyable.

Chuck watched Lucifer pace back and forth. It still disconcerted him, how Castiel's body (Hell, if he really wanted to be accurate it was Jimmy Novak's body...) fell into that extra predatory stance, how his face twisted with unfamiliar expressions. Especially comparing the last time Chuck had been around Castiel. But… so things went, in his life. People changed, or turned out not to be who they claimed, or… stole manuscripts… Showed up on his doorstep either to kill him or stop him being killed-he felt like the protagonist of one of his own shitty novels.

"Are you going to walk back and forth forever, or what?"

Lucifer eyed him, but didn't stop pacing-at least it was a slow pace, and not some frantic to-and-fro. "Are you annoyed?"

Chuck frowned.

"Listen," Lucifer finally came to a standstill. "I don't want to be here any more than you do." He took a step closer, so he could reach out. His outstretched arm left Chuck feeling a strange projection of hostility and fondness, as if Lucifer were going to both slap and caress his face. Simultaneously if possible.

As Chuck thought that, Lucifer grimaced. His fingers curled in a decidedly predatory manner, spider-like and not as smooth as his normal movements. His grimace carved creases into his forehead, the sides of his nose, his eyes. He even seemed labored, out of breath... as if he needed air in the first place.

Chuck tilted his head. "Are you… constipated?"

"You—!" Lucifer curled his fingers into a fist, just a hairsbreadth away from Chuck's nose. "Foul, pathetic waste of flesh…" His chest expanded with a deeply frustrated breath. "Why can't I hurt you…?"

"I told you!" Chuck raised his eyebrows. "You're the only archangel and your duty as an archangel is to—"

Lucifer's cold glare cut him off.

"...told you so…"

Lucifer rolled his eyes. "Perhaps." He crossed his arms. "Perhaps you were right, and… Perhaps I can't harm you, but I can still leave you there."

"What!" Chuck squirmed in the chair, tugging at his wrists as though the tie would loosen. "You wouldn't leave me here! I—I uh… Hm."

A silence fell between them, as Chuck considered his lack of options and Lucifer watched him. Outside, the sun had begun to set and the light peeked through the blinds, silhouetting everything in a strong, clean gold. It turned Lucifer's... Castiel's... hair into a deep amber at the edges, and his eyes the color of the ocean.

Chuck looked down at the floor between his feet.

"I don't want to be left here."

Off in the distance, a dog barked. The slight noise of traffic filtered in through a barely open window in the kitchen.

Without a word, Lucifer turned Castiel's back to Chuck. Hands folded, posture straight. He spoke quietly, slowly—"I've realized I don't think I have the energy to be here." He paused, almost seemed to laugh. "Not that I will disappear, but that I am… tired." He looked over his shoulder. "Are you tired?"

"Oh, I'm always tired." Chuck nodded energetically, as if a firm affirmation might get him on the Devil's good side.

Lucifer sighed. After a moment he came over to Chuck again. He didn't touch him, or try again to harm him. Just loosened the knot so that Chuck was able to tug his wrists free-he nearly fell out of the chair trying to stand, and Lucifer looked on with the vaguest expression of distaste. Raised eyebrows and pursed lips.

Chuck turned to face him and raised his hands in front of him, half in supplication and half in self-defense. "Thank you, I think. Um… would you mind leaving? Preferably forever?"

"You're a waste of time."

Awkward silence.

Lucifer lashed out toward Chuck, with no warning-like a lazy snake striking from the grass. Before his hand could connect, he twisted back with a hiss and a grimace, hand contorting as if his muscles had seized up. He swore, under his breath-most unangelic-and shot Chuck one last glare. Shook his head, raised a hand. He snapped his fingers and the room was engulfed in blue-white light and thick smoke much like that from dry ice or a fog machine. Freezing and cloying.

Holding in a cough, Chuck felt his way toward the nearest window. He threw it open wide, not really minding that bugs would come in through the screen-less opening. He slid or pushed open every window he could find, and turned on the kitchen fan for good measure.

Alone again, thankfully… but shivering and trying not to breathe the almost sulfur-like smell filling the house.

"Shit…" Chuck made his way out to the front porch, into the yard where, though it was dark and dampening, he could breathe fresh air. The moon was large and full in the sky, like a new quarter from a roll of forty. He stared up at it, as his shivers dissipated.

That dog in the distance was still barking, but he didn't mind much.

Note:

I haven't been keeping up with season 11. At the time of writing this I've seen the first three episodes, episode 20, 21, and the finale. So at the time I wrote this I did not know anything about Casifer, but still thought I would enjoy approaching an idea me and a friend had a conversation about over Skype. So aspects of Lucifer!Castiel in this may not be entirely correct based on the show's canon.

Many thanks and large amounts of credit to Mixgoldenphoenix for the idea.