Whenever he'd thought about it--and he had thought about it, with an almost embarrassing frequency--Dean had always assumed that Cas trying to use dirty talk would be either hilarious or so unbelievably awkward that it would put an immediate end to whatever kinky shit they were doing. He'd imagined hours spent whispering profane praises in Cas' ear, fantasized about coaching the right phrases out of him, jerked off to the mental image of Cas stumbling over words he'd never had a reason to say before.
He'd never even considered this.
Cas moves above him, hands gentle with near reverence as he pushes Dean's legs open and up. He presses a kiss to Dean's knee, licks a stripe up the inside of his thigh. The muscles under his lips tremble, and Cas smiles and says, "When your body was decaying in the grave, I took it in my hands and reformed it. I reshaped your broken bones so that they would be strong enough to take the brunt of what I knew I would ask you to bear."
His voice is impossibly low, each rough syllable thrumming indecent warmth into the pit of Dean's stomach. He sucks a mark into the crease between hip and thigh, and Dean swallows back an embarrassingly high sound and twists his fingers in white sheets and dark hair. Cas speaks slowly, precisely, and Dean has done some downright naughty things in his life, but when Cas tongues at the divot of his navel and says, "I held your soul in my possession and purposefully left my mark so that all who looked upon it would know that I was the one who raised you from damnation. You are my masterpiece and my signature is etched into every cell in your body, written into your very DNA," Dean nearly comes without even being touched, like he's fifteen and Carol Taylor just let him get to second base for the first time.
"I brought you back clean and pure, and I take an unholy delight in making you dirty." Deceptively soft hands curl around his calves and coax his knees open wider. Cas looks up at him with dark, half lidded eyes, not looking away even as he moves further down the bed and spreads Dean's ass cheeks apart. His gaze only drops when his head does, and Dean would be disappointed, except that's the flat of Cas' tongue licking slowly over the pucker of his hole. It's wet and dirty and just the right side of invasive, and Dean nearly chokes on his own tongue at the first thrust of Cas'. Instead, he hooks a leg over Cas' shoulder and pushes back against the hot, filthy mouth that's working him open into a slick, sloppy mess.
Dean's babbling broken nonsense, his nails digging painful crescents into the calloused flesh of his palms, when Cas pulls away, his lush lips red and swollen and slick with spit.
There's a hint of a smile playing around the corners of Cas' mouth and his stubble scratches when he presses his cheek to Dean's stomach and says, "I mapped out the intricate labyrinth that is your nervous system, fitting each neuron into its place, so that you could perfectly feel the spark of every miniscule touch as I take you apart like this."
A long, elegant finger pushes inside of him, crooking just exactly right. Dean shouts a curse and bucks his hips. His cock bounces against his stomach, almost painfully hard and dripping with precome despite how Cas is ignoring it.
"Please," Dean begs. His voice is thin and needy in a way he doesn't recognize, but Cas has two fingers in his ass now and he bites down on a nipple just hard enough to make Dean arch up into it with a gasp, and he doesn't even care what he sounds like, can't work up a single shred of shame, just keeps repeating, "Please, please, please."
It's winter in Michigan, but the room feels almost oppressively hot, and Cas' body and words slide over sweat damp skin as he moves to scrape his teeth along the long, vulnerable line of Dean's neck.
"I was supposed to bring you back the way you were, but I made you better. Do you feel how fast your heart is beating? Do you know about the tiny imperfection you had in one of your arteries? Your heart could have given out at any moment before, but I crafted it to be perfect. Let it race, let me feel it pounding in your chest, all the way down to where I'm buried inside of you."
Dean nods, beyond actual words, barely able to grunt out desperate little noises that sound like shards of broken pleas, and then Cas' fingers are sliding out of him, leaving him feeling achingly empty. But not for long, because Cas is good and merciful and pushing into him slow and smooth, and he's barely bottomed out before Dean is shaking and coming in long streaks all over his stomach. Cas smiles down at him, his hair curling at the ends and falling in his eyes and his fingers tight around Dean's hips, his thumbs pressing perfectly into the shallow hollows above Dean's hipbones. He smiles and it's all teeth, and then he starts to move.
"Oh, shit," Dean tries to say, though he thinks it probably comes out more like, "Shuuugh."
Cas leans forward, nearly bending him in half in a way that would have Dean shoving and glaring at anyone else. But Cas is hitting his prostate with each hard thrust and his lips are hot and soft where they brush against the shell of his ear when he says, "I know your body better than anyone else ever could. I have you memorized inside and out, and were I given a hundred lifetimes I cannot fathom ever growing tired of this."
And Dean isn't some hormonal kid who gets stiff from a good breeze, physically can't get it up again so soon, but Cas rips another orgasm out of him, dry and almost painful, and when Cas comes and collapses on top of him, Dean can't even work up the energy to bitch about the fact that he's laying in the wet spot.