A/N: Title translates to When the Angels Fall. This is also the title of a song by Lyriel ft Thomas Lindner that's stunningly beautiful!

Anywho, this is a tag for 13x22, so spoiler alert. The twist for this fic is that Sam actually witnessed the Cas vs alt!Cas showdown. I have a lot of feelings. Basically it's just an angst-fest. Thanks to Aini NuFire for beta-ing this for me! :)

Sam isn't sure what disturbs him more. Whether it's the sight of the angel Cas is fighting—the one wearing his face—or the words that they speak.

"Don't think you are better than me. We are the same."

"Yes… we are."

Maybe it's the image of Cas plunging the blade hilt deep into his enemy, the image of Cas dying. Even though it's the wrong Castiel, the pain is still too near from when it was their own. Or maybe it's the utter lack of hesitation, that Cas doesn't even flinch before killing this version of himself. Maybe it's how his expression, when he turns and sees Sam watching in horror, is empty as cold stone.

Sam doesn't tell Dean what he saw, the other Castiel, and neither does Cas.

...

Sam isn't sure what saddens him more. Whether it's Gabriel's sacrifice, or Cas's face when the portal closes and his brother hasn't come through. And Sam knows that Cas knows. They had just gotten Gabriel back, just started to see the archangel he could become, and now he's gone.

Or maybe it's the perfect stillness with which Cas holds himself as Bobby honors their fallen brothers and welcomes the new ones: Sam and Dean.

Only Sam and Dean.

Cas is an angel, and he might have helped them all escape, fought just as hard as the Winchesters, but he isn't welcomed and his brother isn't among those they mourn. But Cas doesn't say a word, of course he doesn't, because he never does. He doesn't ask for recognition or praise. He doesn't expect thanks for doing what's right. He doesn't demand acceptance as one of them.

But Sam knows how desperately he aches for it, even if he's never said the words. Hell, Cas probably doesn't even know that he deserves it.

So when the gathered hunters continue to mingle and Cas silently excuses himself, Sam gives him a moment. And then he follows his friend's footsteps outside to the night-lit field.

To his alarm, Cas is kneeling on the ground, slumped forward and head bowed with his fingers clenched in his hair. His body trembles, silhouetted against a pale-faced moon. He's broken.

Sam kneels down beside him and touches the angel's shoulder.

"Cas-"

"Leave me."

For a second, Sam pulls away in shock at the guttural words, spat out through clenched teeth and a pit of agony. Cas isn't looking at him. Sam doesn't leave. Carefully, he sets his hand back down on the angel's arm.

"What's wrong?"

"What's wrong- where do I start?" His voice rises, and when he finally lifts his gaze, Cas's eyes are already red-rimmed and glassy.

It makes Sam's own eyes begin to water, because in that moment he sees that the depths of Cas's pain is a bottomless well. And he, tiny human, can't begin to fill that hole.

"I'm sorry," he says anyway. "Cas, I'm so sorry about Gabriel. I know the angels were hoping he could fix Heaven-"

"You're sorry?" Cas spits out, pulling away again. He climbs to his feet, fists clenched. "You're sorry, because he could have fixed Heaven?"

"Cas-"

"Sometimes, Sam, when we mourn someone, it's because we loved them, not because of what they can no longer do for us!"

"I didn't mean-"

"He was more than just a weapon! Gabriel wasn't just valued because he could have been useful! He meant something, beyond just a function! Gabriel mattered."

Cas's shoulders are heaving and Sam feels like shit. Partly because he truly didn't mean to imply what Cas is saying. Partly because he suspects Cas isn't just talking about Gabriel. Holding his hands out, Sam shakes his head.

"Yes. He did. He did, Cas. Gabriel died a hero. And that's how he'll be remembered."

Cas stares at him. There's something almost manic in his eyes, and Sam can't remember seeing their steadfast friend so out of control before. Grief is driving him to a dark place; god, how Sam knows that feeling. After a moment, Cas simply replies,

"Gabriel won't be remembered. When the last of the angels are gone..." He looks past Sam towards the Bunker, where the hunters are inside mourning their own dead. "No one will pour a drink out for Gabriel," he murmurs. "No one's going to put his body on a pyre. There won't be anyone left to honor what he sacrificed."

"We will remember him," Sam reminds his friend. He frowns and shakes his head, taking a step closer and wishing he can put together all the broken pieces of the angel who's given everything to protect them. "Cas, talk to me."

This time, Cas turns his back. The moonlight disappears behind a cloud, and the world darkens. "I saw you there, Sam," the angel finally growls. "I know you saw him, too."

He's had a feeling this was what was fueling Cas's emotions. Sam tries and fails to forget the sight of that other Castiel, the evil one, spurting grace on the end of his doppelgänger's blade. He takes a breath. "Cas, you're nothing like him-"

"I'm exactly like him."

"No," Sam argues, needing his friend to believe him, to understand. "He was evil."

"Why was he evil?"

Was Cas serious? Sam stares at the angel's back and splutters, "He tortured Charlie, he tortured a lot of humans-"

"I tortured a human!" Cas shouts, cutting Sam off. His confession fills the darkness as he whirls back around. Even in the black night, his shame bears itself for the world to see. The rawness in his pain could bleed Sam where he stands. "I stood over him, felt his fear, put my hands to his head, and-" The angel squeezes his eyes shut. He's trembling again. "I tortured that man."

"No, that's… that's different-"

"Why? Why is it different? The Castiel of that world and I are the same, Sam. The only difference is whose side we're on."

Sam staggers back a pace, though the words aren't delivered as an accusation so much as resignation. For a second he can't breathe, and his eyes burn. It's just hit him that back when Cas was still on board with Heaven—arguably at his worst—he had still told Dean that he would give anything to not have the hunter torture Alastair.

Because Cas understands what it means to torture, the atrocity of the act. He's always despised the very idea. Even as he's doing it, as he has before, to save a Winchester. And they hadn't even considered that it would bother him to be ordered to torture that man, like he was their attack dog.

"Cas… I am… I'm so sorry."

"It doesn't matter, Sam. I could have refused, but I made my choice. He and I, we both made the same choices." Cas pauses, then snorts and mutters almost under his breath, "It seems every version of me is doomed to fail."

"You didn't. Listen to me, that Castiel, he would have kept hurting people. Killing them. Helping Michael enslave them." Sam thinks again of that familiar face, yet the face of a complete stranger, and his heart quails to imagine their Cas ever looking like that. "I'm sure that seeing him was horrible for you, Cas. But you won. The version of you that chose humanity was the stronger one. You killed an evil angel."

This time, it's Cas's turn to take a step back, and his eyes are swimming again, glassy as a breeze brushes between the pair. It sends a chill through Sam's body, or maybe that's from the disbelief on Cas's face.

"Is… is that what you saw?"

"Cas…"

"You really don't understand. Sam, you- Yes, he did evil things. But he was me. He was what I could have—would have—become."

Sam reaches out for the angel, clutches his arm. "No. You're stronger than he was. You're good. You believed in humanity, enough to rebel for them."

"So did he!" Cas cries. He doesn't pull away, but he seems to have no energy left to do so. "You were right there, but you missed everything! Have you forgotten what set that world apart from ours? It was you. He didn't have you and Dean to give him that final push to leave Heaven! He never escaped from Michael!"

"He still could have refused-"

"He did! And they destroyed him!"

Silence falls. Two hearts pound in the darkness, sharing pain that transcends words. Sam studies Cas, sees the conviction, but can't share it. Not yet. He knows Cas doesn't want to believe that maybe this version of himself really was just evil like the other angels; Sam wouldn't want to, either, but he lived with that fear for years.

Cas shudders. "He… he ran."

Sam doesn't follow his friend's line of thought. "He was outnumbered. I don't see-"

"No! Sam, he ran. To a truck. Why was he escaping in a truck?" Desperation and despair dance through the depths of Cas's eyes as the clouds shift away once again to illuminate his lined face.

And then realization strikes. Once again, Sam can't breathe. The implications have been there all along, but he's been so busy with his revulsion of that Castiel, Sam missed the most obvious fact. And now that he sees it, Sam would give anything to forget, to return to blissful not-knowing.

It's been so long since his Cas has been able to fly that he almost forgets angels are supposed to. That in the other world, they can. All of them.

All of them but Castiel, who was left to flee however he could.

Sam draws a ragged breath. "They took his wings…"

Cas's voice is haunted. "They took everything."

Pieces continue to connect. How the other Castiel must have rebelled. How severely the other Michael must have punished him for it, infinitely more cruel than their own Michael had been. The strange tics and twitches, almost as though a spicule had been driven into his brain too many times to make him obedient. Again, and again, and again, and again, because he had continued to resist.

Maybe just enough times to finally break his mind apart.

"They destroyed him," Cas repeats, starting to shake harder, masked in grief and something Sam can't identify. "They broke him over and over until there was nothing left of him. And then they put back the pieces they could still use. They made him an instrument of everything he stood against. So no, Sam. Maybe you saw it as me killing an evil angel. I saw it as mercy. Because I know what he would have wanted."

He sinks to his knees, and Sam goes with him, as Cas whispers,

"Because we're the same."

Sam doesn't know how to respond to this. His mind travels shrouded byways for just a moment, just to imagine if Cas hadn't ended up coming with him and Dean… if he, like the other Castiel, hadn't escaped Heaven. He imagined their Cas being torn open and reshaped until all that remained was the deranged soldier who would kill the same humans he'd sworn to protect.

And Sam finds himself clinging to his angel, hands fisted in the tan overcoat, like he will never let go. Because he won't. Because the idea of losing Cas like that is worse than the idea of dying at the teeth of the vampire den.

"He was alone…" Cas chokes and Sam realizes the angel is sobbing. "He suffered more at their hands than I ever did, yet he'll be remembered as the evil angel I was lucky enough to defeat. He had nothing. He had no one. They didn't care about him, only what he could do. And he did horrible things, but Sam… can you imagine, for even a moment…"

He chokes off. But now Sam recognizes what else lingers in Cas's drawn face, not only grief for what his counterpart suffered, but a horrifying loneliness so vast it threatens to swallow him whole.

A beloved brother, fallen in battle and unrecognized by the humans he had saved…

An alternate version of himself, tortured and wrecked and then used because he'd had no one to save him…

A Heaven on the brink of death because the angels were almost gone, the entire species verging on extinction…

Eyes still clenched closed, Cas whispers to the midnight air, "Sometimes, Sam, I just can't see the point anymore." Then, before the hunter can think of anything remotely comforting to say, he growls out, "Just… leave me." He pushes away, rises to his feet, turns.

Sam watches the angel trudge a few feet away, then stare up at the stars. He considers his next move before urging, "Wait here."

Cas doesn't twitch, so Sam hurries back inside, hoping no one notices if his eyes are red. He dodges a few hunters loitering in the hall, catching sight of Dean at one end with Bobby but not motioning him over. Maybe he'll catch Dean up later. Maybe this will stay between him and Cas. For now, he doesn't want Cas to have to repeat all of that again while the pain is so near, so he simply grabs a couple of beers from the kitchen and makes his way back to the grass outside where he left their angel.

Cas is marble and granite, unmoving from his pose. Sam steps up to join him and wordlessly gazes at the heavens while holding out one of the bottles for Cas to take. The angel sighs.

"Sam, I don't want-"

"Do you trust me?"

Again, Cas sighs. "Yes."

Sam nudges the bottle into Cas's hand, then opens his own. Instead of drinking it, his arm extends out, then tips. Beer splashes the ground. "To Gabriel."

Cas falls still. A frog croaking in the distance disrupts the solemnity, but somehow that's fitting. Slowly, the angel twists the top off his own bottle and pours some of the liquid out. "To Gabriel," he whispers.

Again, Sam tips his beer, spilling some more. "To Castiel."

This time, his friend is shaky in his movements, but he copies Sam. "To… to Castiel."

Sam doesn't know if this is helping or not, but Winchesters aren't so great with comfort and he's doing the only thing he knows how. His heart clenches as he thinks again of the brave, fallen angels. When he holds up his bottle now, he doesn't pour it out. Instead, he toasts, "And to you, Cas."

The angel doesn't answer, but when Sam clinks their bottles together, he does at least drink. They fall silent after that, just watching the skies. It's chilly, but the hunter isn't about to suggest going back inside where Cas will be the outsider even though this is his home. No, Cas has borne worse than a little bit of cold for him. Sam accepts the chill as a small price to pay for still having his best friend at his side.

"I know it seems hopeless," he finally says after several companionable moments. "Believe me, I get it. I've been there so many times. When we lost you…" Sam's breath stutters, then he pulls himself together. "And this is a thankless job. I'm not gonna tell you it gets better. And you're right, that other Castiel… he didn't have me and Dean. But you do. No matter what happens, if Michael comes through, or if Heaven falls, or if you become the last angel standing, we'll be here with you. Cas, we'd follow you to the ends of the earth. Both of us."

Cas doesn't reply, but Sam catches his friend's side-eyed look in his periphery.

"But Cas, you have to promise. You have to promise me you'll always keep fighting. Everything you said about Gabriel was true, but not just for him. You matter. Not because of what you can do, but because you're our brother and we love you."

The angel lowers his head. Sam can see how drained he is, broken down by the emotions he always keeps behind such carefully constructed walls. Letting it out will be good for him, and there's no one else out here to see. Sam settles his free hand on Cas's shoulder and squeezes.

"We're going to do right by Gabriel," he assures his friend. "And if we've learned one thing, it's that there's always a way, if we stick together. You're not alone."

Cas continues his silence, sipping the beer. Crickets sing, stars glow, and the world spins on. Sam is content to remain quiet after that, give Cas as much time as he needs, but finally the angel says,

"I promise."

Sam glances at him.

Cas takes a breath. "To keep fighting. It's what I was made to do, anyway."

On this point, Sam can't help but disagree. A sad smile tweaks at his lips. "No. You were made to choose for yourself."

Cas holds his gaze. Sam sees pain that he wishes he can take away, but he also sees strength. He knows Cas will endure. Cas is that kind of guy. But he won't have to do it on his own, because he does have the family he's always wanted. Sam will make sure he knows that.

After another thoughtful moment, Cas supplies,

"Then I'll choose to keep fighting."

Sam's smile smooths. "I know." He tips his beer in Cas's direction again in a toast, and while the angel doesn't smile back, some of the anguish disappears from his eyes.

"Sam. Thank you."

Sam squeezes his shoulder one more time, then lets his hand fall to his side as they drink. No more words pass between them, content to just be. Sam knows what it's like to be broken. He knows what it's like to fall.

And he knows what it's like to have someone waiting there to catch him. So he'll be waiting as well, to catch their angel whenever he falls.