Dean, Sam, and Cas find a very interesting mirror- it comes with a curse. Destiel.

"I found a new door!" Dean shouted, his voice echoing through three layers of rooms within rooms.

"Shouldn't we have run out of those?" San asked, coming to investigate anyway.

The door, a small, dark, unassuming rectangle door, was locked tight.

"You think it's locked from the inside?" wondered Dean.

"Or glued," Sam said. "CAS!"

Cas had, apparently, been following Sam to the room already. He rounded the corner and placed a hand on the door, and it shattered under his touch.

"Thanks," Dean said, grinning at Cas. "You first." He gestured at the dark and foreboding doorway.

Sam rolled his eyes and flipped the light switch.

"A mirror?"

"It must be important," Cas reasoned. "Or it would not be here."

"The inscription's not Latin," Sam said. "Or any language I recognize."

"Fun," Dean said, running his hands around the edge. "Magic mirror? Secretly a portal? What do you think?" He jabbed gingerly at the dusty, silvered surface. Solid.

"Lemme grab a rag," Sam said, and darted away. He returned with a rag and windex, and began cleaning the mirror.

"It's just a mirror," said Dean.

"Shush. I haven't cleaned it all."

Dean tilted his head sideways and ran his fingers around the whorls in the metal frame. Sam dusted the bottom. Cas watched.

Sam stood, pushing away Dean, and looked into the center of the mirror.

"It's just a mirror," repeated Dean. "Mirror, mirror, on the wall-"

"Shut up, Dean!" Sam snapped.

"Whoa, dude, chill. What-"

"I said, shut UP!" Sam yelled. He examined the mirror.

"Sammy… what do you see?"

"Jess," breathed Sam.

Dean swore he felt his heart break.

"What is Jess doing?" Cas asked carefully.

Sam wordlessly raised his hand to his shoulder. Finding nothing there, his face fell.

"Sam?" Cas asked.

"Of course it- of course it wouldn't be her, not really," Sam said, much quieter. But he didn't move.

"Sam…" having dealt with the supernatural for a long time, Dean recognized this mirror's trap. Sam loved Jess, so he got Jess, as long as he looked in the mirror.

"Sammy, walk over here. Leave the mirror alone." Dean spoke as if to a scared animal.

"No," Sam said.

"Sam!"

"No, Dean- Dean, it's Jess…"

"Sam, the mirror! It's trapping you!"

"What if- what if it shows the future?" Sam asked, anguished. "She looks older- if we somehow got her back- I'm a little older- we have a little apartment-"

"Sam, it's not real…"

Sam clenched his jaw. "You're right."

"Look at me."

Sam did.

"Walk away."

Sam did, leaving Cas standing in front of the mirror.

"Maybe we should- Cas?"

"I suppose the mirror works on angels," Cas said, in a little bit of a choked voice.

"What do you see, Cas?"

"All my brothers and sisters are alive, and God is leading us." Cas turned away with effort. "But it is pointless. Fantasy, of course," he said. "We should cover this mirror."

"Exactly," Dean agreed, because that had been what he was going to suggest. Cas walked to the brothers, and the three of them walked out the door.

Cas and Sam didn't look back.

Dean couldn't resist.

"No, Dean," Cas said, tugging on Dean's wrist, but Dean frowned.

"What were you two on?" he asked.

"Dean?" Sam asked. "Uh, what do you see?"

"Me. You. Cas. It's normal."

"Perhaps you are immune?" suggested Cas, dropping Dean's hand and walking to peer over his shoulder.

Sam bobbed back and forth. "Is it reflecting me?"

"Yes, you idiot. You look like a headless chicken."

Cas wasn't looking at Sam. He was staring down by Dean's side.

At his hand.

At his wrist still clutched in an invisible Cas's grip.

"Dean," Cas said softly. The sound echoed around the room- all sounds had, you couldn't tell where they came from. "Where am I?"

"What d'you mean-" Dean began indignantly, but he turned to the side and Cas wasn't there.

"Cas?" Dean asked, spinning rapidly to face Cas. "When did you move?"

"A minute or so ago," Cas admitted.

"You're still here in the mirror," Dean said casually, pointing to the air right next to him. Watching the mirror, he raised his hand and touched empty air. Cas and Sam could only assume there was a person there in the mirror.

"So weird," Dean said, prodding something. "My hand goes right through."

"I'm not there," said Cas.

Sam stepped forward to peer over Dean's shoulder. Dean turned to look at him. "Can I help you?"

"You saw me move?"

"Yeah."

"Well, it doesn't work unless you're in the right spot," said Sam. "All I can see is a totally normal reflection."

Dean looked down at his brother's collarbone. "What's that line, there?"

"Werewolf hunt went bad when we were kids," Sam said. "Remember? Montana? Hospital?"

"How could I forget?" Dean asked. "See, it's not in the mirror."

"It's not?" Sam asked curiously. He could see it.

"Yeah. Actually, your skin is a little less scarred all over. And Cas is still here." Dean pointed to his side.

Cas walked over to the spot Dean indicated. "Here?"

"Yeah, there. Hey, you're reflecting again!"

Cas walked away.

"Now you aren't. Your reflection stayed here. It nods a little when I say stuff, sometimes."

Cas walked back.

"Thanks," Dean said. "It looks normal now. Nah, what?" He tapped a hand to his shoulder. "What the hell? Your reflection just put its arm around me!"

Cas placed an arm gently aound Dean's shoulders. "Like this?" he asked, frowning.

"Yeah, like that. That's trippy," Dean said, stepping forward and out of Cas's arm. Cas let it fall slowly. Dean broke the mirror's hold on him by moving, and he pressed the glass of the mirror. "It feels like a normal mirror."

"Most magic mirrors do, Dean," said Sam, noting the ease with which Dean had stepped away from his vision. Sam still remembered the image like a drug he was hooked on.

Dean traced the letters again. "Nothing on the inscription? Let's check the archives."

Cas and Sam, equally curious, followed.

"Here. Under 'Mirror.' 'Mirror of Erised,'" said Sam, some time later.

"What's it do?

"It shows… it shows your deepest desire."

"Oh," said Cas.

"What, that was my deepest desire?" Dean asked. "For Sam to have less scars and for Cas to stand next to me?"

"More abstract concepts, perhaps?" suggested Cas. "If Sam doesn't have a scar, it means he did not get hurt. If he did not get hurt, either he did not hunt or he simply wasn't injured."

"Oh. That, that makes sense."

"However, that you would wish for my proximity… you constantly remind me to keep a proper distance. Personal space. It is odd."

Sam, however, knew better.

He stood up. "Hey, Dean… something I wanna talk to you about."

"What?" Dean asked. "We're in the middle of psychoanalysis a la Cas!"

"Come ON," Sam said, and herded his brother out. "Give us a minute, Cas."

Cas sat in confusion as Sam and Dean moved into the next room, out of earshot.

"You LIKE him!" Sam hissed suddenly.

"Yeah, sure. I like you too. We're all family."

Sam rolled his eyes. "No. You LIKE like him."

"Sorry? Like like? Are you in kindergarten?"

If Sam rolled his eyes again, he might never get them down, Dean thought. "You. Have feelings. For Cas."

"Yeah, the friend kind."

"Bullshit."

"Sorry?" And Dean really did sound bemused. How deep has he hidden his feelings, Sam wondered?

"You want to kiss him and have him as your boyfriend," Sam said, thinking that putting it bluntly would help.

"Uh, no." No.

Sam had expected more of a confession than an outright, honest denial, really. Now that he thought about it, he hadn't really had any kind of proper plan.

And what about Cas, anyway? It was no good knowing Dean liked Cas if Cas didn't return the feelings.

So Sam said, "Think about it. Think about kissing him or whatever. Bye." and left.

No, there had been a reason Sam was so sure about Dean and Cas, and it wasn't the mirror. It was lots of little things, like the intense staring and the "profound bond" and the fact that Dean had kept Cas's trench coat when he died- he kept his feathers, too, although Cas suggested that the feathers meant nothing, he was just molting, and probably Dean should burn them. If they needed one for a rare spell, he said, he could always pluck one or two.

But he should talk to Cas anyway, Sam thought.

"Cas!" Sam said brightly, sitting down. "What do you think of Dean?"

"What do I…? What is the reason for this question?"

"Just answer it. What do you think of him?"

"His looks? His attitude? His personality? His biblical significance? His actions, or choices? There are many ways to define a person."

"The first three," said Sam.

"I think he is a good man," decided Cas. "His looks… he appears to be attractive. By human standards."

Sam thought the last three words had seemed kind of tacked on.

"He has a nice soul. He always has. He thinks he doesn't, but he shouldn't think that."

"Do you like him?" asked Sam.

"Yes. We are family, he said so himself."

"Do angels ever date humans?" Sam asked.

"Nephilim are forbidden and unholy," Cas reminded him.

"Yeah, but what if there was never a Nephilim?"

"Angels have dated humans… but it has always resulted in Nephilim."

"Why?"

"Because, as with humans, when a man and a woman-"

"Stop!" Sam hissed. "I, uh, I'm aware." he sighed, and added, "Apparently angels have no control."

"Usually, the purpose is to create a Nephilim."

"Not just... y'know, for love?"

"Angels don't love humans."

"Why?" And why was this turning into angel Q&A?

"Because… Because they do not. They do not love humans in the way you mean."

"Why?"

"I do not know, Sam. I do not know of a single angel who has loved a human."

"How many angels do you know who gave up heaven for a human?"

"No angel would do that," Cas said dismissively.

"Cas, you did that," Sam reminded him.

"Oh. Yes. I did. I am not always an angel."

"Maybe you'd love a human."

"Perhaps I could love a human," Cas agreed. "Although, I doubt I would love a human. I do not meet many. I get to know even less."

"You know me and Dean."

"You are like my brother, Sam."

"What about Dean?"

"He is-"

But Cas stopped.

Sam waited.

"Sam," Cas said urgently.

"What?"

"Am I in love with Dean?"

"Probably," said Sam. "Think on it." And he left to go back to Dean.

"Sam, you are not helpful!" said Cas.

"I think I'm very helpful!" returned Sam.

"You talked to Cas?" Dean asked, sounding somewhat stricken.

"Yeah, so?"

"What did you talk about?"

"Angels."

Dean narrowed his eyes.

"I was bored waiting, so we cleared some things up about angel lore. Anyway, how are you?"

"You cursed me," muttered Dean.

"How so?" asked Sam, amused.

"I can't stop thinking."

"About Caaaaaaaas?"

"It's not funny!" Dean growled. "I like girls, anyway."

"It's called bisexuality," said Sam. "Girls and guys. Cas isn't really a guy, anyway. He's an angel."

"It's- I- I hate you, Samuel Winchester."

"So," said Sam. "Would you, or would you not, kiss Cas?"

"He's my FRIEND," repeated Dean, but the argument sounded weak.

"Yes or no?"

"He's an angel, I'm a hunter, we aren't supposed to like each other."

"Yes or no, Dean?"

"Yes, okay? Yes! But he wouldn't, so it doesn't matter."

"Hm," said Sam, and left.

"I feel like I'm trapped in the elementary school game of 'Tell her I said,'" complained Sam.

"You chose to do this," said Cas.

"Do you love Dean?" Sam asked.

"…Yes."

"Oh, good," Sam said. "You should go over there and kiss him."

"What if he does not reciprocate my feelings?"

"Cas, trust me, he does," Sam said, and left.

Sam found an old bedsheet and draped it over the mirror. On it, he wrote, "Mirror of Erised. Exercise caution." He then cleaned up the door.

When he got back, nobody was in the room Cas was in, so he took it as a good sign and left. Hopefully, it would work out in the end.

Earlier:

"Dean?" Cas asked, stepping inside the room.

"Where's Sam?" Dean asked, turning to deliberately avoid Cas's gaze. He made a show of looking for his asshole little brother.

"He left," said Cas, standing somewhat awkwardly.

"Oh," said Dean. "Just you and me, then."

"Yes."

"Did you ever figure out the mirror?" Cas asked, suddenly realizing why his figure hadn't moved from Dean's side- of course, Sam's last words to him had been the truth.

"Yeah," Dean said, grinning. "It- uh-"

But he wasn't going to tell Cas what it meant, Dean realized. "Yeah. Finally."

"Oh, good," Cas said, and with a stronger conviction now, he stepped forward and kissed Dean.

Dean froze.

And then, with enthusiasm, he reciprocated.

"I guess it's pretty obvious what the mirror says, huh?" Dean asked.

Cas nodded. "Perhaps it will reflect me now."

"We'll never find out," Dean decided. "We're done with the mirror. Thanks, mirror."

"Thanks, mirror," echoed Cas. And then: "but kissing is better than simply holding your hand."

Dean grinned and kissed him again.

Oh wow is this a Mirror of Erised AU

I'm sure no one has evvvver come up with this idea before

Note from your author: Matchmaker, matchmaker, make me a match... who else has that one Samlike friend?