After the end, they stay together.
Sam and Dean are dead, but the gates are shut and their work is done, so God allows them to move on for good. Meg, protected by her angel, is the one who finds them. She wraps them up and burns them side by side outside their bunker. Castiel appears as she watches the flames. He does not speak until their bodies are ashes and the fire has burned itself out.
"What will you do?" he asks, not looking at her.
"Everything," she answers.
.
She doesn't know why he stays. She thinks maybe because she's familiar for him, the last bit of familiarity in his world now that Sam and Dean are gone. Another part of her thinks it's some form of affection.
Mostly, she thinks that he's just scared to be alone again. She lets him tag along, but doesn't shelter him from her world. She fights and steals and does everything but kill, and he is always one step behind her.
They're somewhere in Ohio when she steals a motorcycle and forces him onto it behind her. She speeds down the highway as fast as the bike will go, hair whipping behind her and the wind stinging her face as he clings to her.
When she glances behind her, for a moment she can see his wings.
She stops on the side of the highway when the bike runs out of gas and walks into a field, not caring if he follows. He does, and tugs her down onto the grass to lie beneath the stars. "It almost felt like flying," he tells her. The stalks of wheat sway in the wind and it makes her sneeze. She turns away from him and does not speak.
.
"Where are you gonna go?" she asks as they walk down a dirt road in Nevada. Castiel gives an almost human shrug.
"Here is as good as anywhere else," he answers.
"Not gonna go back to Heaven?"
He looks away. "No. It would be unpleasant if I were to return right now. I caused a lot of pain."
"We've all fucked up, Clarence," she tells him. "You gotta put on your big girl panties and get over it."
.
They wind up in Washington, and Meg decides she wants to walk to New York for the Hell of it. "We'll go to California first, though," she says. "I wanna go to the beach."
"I could take us there far quicker," he protests.
"Clarence, you have to learn to do things just because," she answers, turning away from the Canadian border.
"It is still an impractical decision," he says. Meg laughs then, for the first time since she nearly died facing Crowley in that alley.
"That's what makes it fun. C'mon, let's go the beach."
.
When they get to California, Meg forces him into a swimsuit and laughs at how uncomfortable he looks, standing at the edge of the water in swim trunks. She changes into her stolen purple bikini and runs into the waves, despite the burning from the saltwater.
"Get in here, Clarence!" she yells, pushing her hair away from her burning face.
"Doesn't it burn you?" he asks, standing waist-high in the water with her. She moves with the waves, ignoring the burning sensation lighting up her stolen flesh.
"Burns like Hell," she tells him, and it does. But the burn is familiar, almost comforting, in a way she can't explain to him. He blinks and she squeals when he picks her up and walks her out of the water. "Fuck, Cas, what was that for?"
"I do not wish to see you in pain," he answers, laying her on the sand. He stares at her with narrowed eyes, and she doesn't have the heart to remind him that her kind revels in pain.
.
They make it halfway across the country before they're spotted by hunters in a seedy, hole-in-the-wall bar. The hunters hear them talking to each other, using their real names, and follow them. When she goes outside to smoke, she steps into a devil's trap.
The first hunter talks about the Winchesters, blaming her for their deaths. The second one asks about her vessel. She glares at them the whole time, until the first one pulls out a book and begins his exorcism.
For the first time in her long, long life as a demon, she's truly terrified. With the gates of Hell shut for good, she has no idea what will happen to her when they finish speaking. She can't use her powers, can't do anything except watch as black smoke begins to leak from her vessel's mouth as she dry-heaves.
Castiel is gonna be so pissed at me, she thinks. Suddenly, she's being forced back into her vessel and the two hunters are lying at her feet.
"Are you hurt?" Castiel asks, stepping into the devil's trap.
She shakes her head. "No. But I think we should get out of dodge fast. Forget what I said about walking. Let's fly." He breaks the trap and touches her forehead. When she opens her eyes, they're in an empty hotel room in New York. "What's up with the fancy bits, Clarence?"
"You need to rest," he says, leading her to the bed. "Sleep. I'll watch over you."
"Anyone ever tell you that's creepy?" she asks, sliding under the covers and letting her vessel's exhaustion creep up on her.
He smiled at her. "Many times."
.
They're ten years into their little adventure when she decides to stop moving and settle somewhere. She gets a little house in Florida and sets it up, playing at being human. Castiel is confused, but stays, settling into the one bedroom, one and a half bathroom house with uneasiness.
It lasts six months before they're on the road again, circling around the states and Canada in a never-ending trek. She's not built to be trapped indoors, playing at being human. Castiel isn't either, she noticed during those six months. She would find him in the yard at all hours of the night, or restlessly pacing the rooms, needing to be out.
"Let's walk to South America," she says one day, reaching out to tug at his hand. He stares at their locked fingers in silence and follows her down the road. "It'll be fun."
.
It's only twenty years into their adventure that Meg starts to feel restless for a kill. Trekking through Greece, she kills a lamia with Castiel next to her, watching silently. After that, she demands to be taken back to the states and drags him on all the hunts she can find.
They visit the bunker, once, during Christmas. Kevin is still there, older and just as paranoid. Meg screams when he douses both of them in holy water, and Castiel drags her out of there while Kevin hollers at them, a wild look in his eyes.
Castiel takes them to a shitty motel two states away and lays her on the bed. "Come here, Clarence," she orders softly. Castiel sits with her and she laughs. "Twenty years into this little partnership and it's the first time I've gotten you into my bed. I'd be roaring with laughter if I wasn't still in pain from the not-so-little prophet dousing me with holy water."
"We never did order that pizza," he says. She laughs again and tugs him down.
.
She takes him skinny dipping in Montana, sledding in New York, and forces him onto a Ferris wheel on the Jersey shore.
They spend an entire winter in the wilderness of Northern Canada, Meg dragging him through the snow piled over their heads and digging out tunnels with him.
"You've never climbed a tree?" she asks, hauling herself up the branches. "Shit, Clarence, get up here."
"I am not sure how," he says, staring up at her. She shimmies down the tree and perches on one of the lower branches.
"Just grab the nearest branch and pull yourself up, feathers." She laughs when he does, feet kicking in the air as he struggles to pull himself up. When he reaches the branch she's on, he stares at her. "Good job. Now let's go higher."
"You are like a squirrel," he comments, watching her scurry up the branches.
"I grew up on a farm, Clarence," she snaps, hooking her legs around a branch and dangling upside down to look at him.
"I was not aware you remembered your human life."
"I just don't talk about it." She rights herself and continues to climb upward until the branches will no longer support her weight. It takes a while, but Castiel makes it up, staying close to the trunk.
They sit in silence, watching the snow fall over the wilderness. "Um, Meg?" he asks.
"What?"
"How do we get down?"
.
"Isn't there anywhere you wanna visit?" she asks, legs dangling from a tree. "You can't follow me around forever."
"I will go, if you wish it," he answers, looking up at her from the ground.
"You can stay. I don't care." She jumps from the branch and lands next to him in the snow. "I think I'd miss you in the bedroom." He narrows his eyes at her and she laughs.
.
They walk the Earth together for a hundred years, hunting and running and watching humanity rise higher and higher until it falls.
"What do you wanna do?" she asks, walking through the ashes of a once-prosperous town.
"Good," he answers, reaching for her hand. She takes it, and he brings them to the places the war has touched. She watches him heal, and watches as villagers and high-end businessmen alike profess their gratitude to him.
"Who's this young lady?" asks an older man in Russia.
"My wife," Castiel answers, healing the man's son. She glares at him, but doesn't challenge it.
.
They change their names in every town they visit. Emmanuel and Rachel visit a small town in Quebec, healing the sick and wounded. Thomas and Leah appear in Hawaii as clouds of ash block out the sun. Alexander and Penelope visit Kansas and walk through the woods, toward the untouched bunker.
Kevin is long gone, and they visit the spot where Meg burned their boys. The clearing is quiet, and so are the hills around them. There is no birdsong as they walk back to the bunker in silence, arms brushing.
"I don't get the point of this," she says. "They're all gonna die, anyway."
"There is no point," he answers.
"You're doing penance," she whispers, stopping in her tracks. "Holy shit, Clarence. You still think you need to make up for all the shit you pulled."
He keeps walking, and she follows him, shaking her head.
.
The war rages, he heals, and she's the one who follows him now, pretending to be human and his wife. Humanity begins to crumble around them, and she watches it without the delight she would've had, once.
They're in a little village in England, healing the sick, when Castiel drags her to the church. He stands outside for a long time before he pulls her in and asks to see the priest.
"Marry us," he requests, taking Meg's hand. She snarls at him and tries to pull away, but he grips her harder.
"You're the third young couple this week," the priest grumbles. "With all the boys going off to war, everyone seems to be jumping into marriage." He agrees to marry them anyway, and Castiel declines a license or anything legal, saying he only wants to be united in the eyes of the Lord.
"I would like you to use your real name," he tells her, standing at the altar. She glares at him and almost refuses. "Meg, please. We have been living in sin. It is time to correct it."
She snorts, but goes through with it, anyway. It doesn't matter, in the end, because she knows he will only teleport her to every church on Earth before she agrees, stubborn as he is.
She hisses her human name at him, and he smiles. When he kisses her, a clean feeling flows through her, and it makes her want to vomit.
.
"I love you," he breathes into her hair, curling an arm around her waist. She stiffens and squirms, trying to dislodge his hand.
"Lying is a sin, Castiel," she says. He tightens his grip.
"Lie to me."
"I've never lied to you," she tells him. The words taste bitter in her mouth, and she rolls away from his touch.
He draws her back to him. "I'm sorry."
.
They're on a formerly-pristine beach somewhere in the Caribbean, strolling by the water, when the absurdity of the situation finally hits her over three hundred years later. An angel and a demon, walking the Earth, healing, marrying, and watching humanity struggle to survive would be hilarious to her if it were someone else. She laughs then, falling to her knees on the wet sand as the grayish waves roll onto the beach and burn her skin.
He looks confused, and she pulls him down with her, pinning him to the sand. She takes him on the abandoned island, a human skull staring at them, half buried on the beach. "What would your Father think of you now?" she asks, after, lying on top of him.
"I don't think he cares," Castiel mutters, stroking her hair. "We should move. The saltwater will hurt you."
"Just stay here for a bit. I'm tired of moving all the time," she tells him, putting her head under his chin. "Lie to me?"
"I love you," he says.
"You, too."
.
They walk the world and watch the last bits of humanity crumble to dust, failing to survive.
"What happens now?" she asks him, legs dangling over the edge of the Grand Canyon.
"I don't know," he answers, sitting next to her. "For now, at least, we are the last two people on Earth."
"We're not people," she mutters, lying down on her back to stare at the smog obscuring the stars.
"If we abandoned our vessels, they would be," he points out.
She snorts. "Abandon our meatsuits and go where?"
"Heaven," he answers, finally lying next to her. "You are my wife, in truth, and now belong with me where I go."
She snorts. "A demon in Heaven, 'cause that makes perfect sense."
"We would all be together again," he says calmly. "You and I, and the Winchesters and their family. All of us."
"Yeah, I don't think you're ready to go back." She rolls onto her side, facing away from him.
"Has it really been that terrible?" he asks.
"No," she says, only half-lying. He falls silent, and she swirls her fingers through the dust on the ground. Three thousand years of partnership and they still can't seem to be completely honest with each other.
.
They watch the world come alive again. She's lost count of the years they've spent, circling the Earth, watching nature reclaim the signs that humans ever existed. The smog clears and the sun shines down on them for the first time in centuries, and Meg bathes in the glow, Castiel beside her, both of them having shed their rotting clothes long ago.
"When we leave our meatsuits, will they even remember anything?" she asks, lying in a grassy clearing.
"I don't think so," he answers. "It's been so long for both of them. Think of it as a fresh start of sorts for them."
"It really is pretty here," she comments, walking to the edge of the clearing and running her fingers through the leaves of the bushes.
"Come lay down," he orders softly. She does, padding back to the middle of the clearing.
"Are you happy?" he asks, pulling her to him.
"It's okay," she says, pillowing her head on his chest. "I could've done without the stabbing and getting shot and torture, but this is pretty sweet." She pauses and takes a breath. "What about you? Think you've finally done your penance?"
"Maybe I have. But now I understand why Anna chose to fall."
"Anna?"
"She was my sister. She tore out her Grace and fell to become human. I understand now," he answers.
"Tell me about her," she requests. He does.
.
They walk through the new world, alone except for each other. The quiet doesn't bother her as much as she thought it would, but it makes Castiel seem restless. There is nothing human left to enjoy, but they still travel endlessly.
She does not recognize the places they visit anymore. Animals graze in the remains of Carthage, where the end began for her. Somewhere in what used to be Japan, she dips her toes into a pool and lets the fish nibble at her toes.
The ocean doesn't burn so much anymore when she pulls Castiel in with her. They walk across the globe, not needing food or rest, determined to see everything as it is reborn.
"Is this what it looked like at first?" she asks, lying in the sun beside a stream in what she thinks used to be India. "Before He made humans?"
"Yes," Castiel answers, walking out of the stream and sitting next to her on the grass.
"It's pretty."
.
She's not sure where they wind up, but she thinks it's the prettiest place they've visited so far. Lush with vegetation and filled with life, they walk through it for days. In the end, they find a clearing with a large, sprawling apple tree, and Castiel lays on his back under it, closing his eyes in the shade.
Meg runs her fingers over the trunk. "He's remade it, hasn't He? Like in the stories?"
"Maybe. But He has returned. I feel it." He opens one eye and looks at her. "Come lay down."
"You going, then?" she asks, lying next to him in the shade.
"We are," he corrects. "It's time."
She snorts. "We're goin' to Heaven, Clarence."
He chuckles softly, pulling her close to him. "It appears you were right in Carthage." They fall silent, then, and she pillows her head on his chest, eyes drooping.
"Hey, Castiel?"
"Hmm?" he mumbles, his voice heavy with sleep.
"Lie to me."
He kisses the top of her head. "I don't love you."