Thank you so much for the prompt!  Apologies for taking so long to answer, but I hope you like it.  Read it below, or on AO3 for full tags and warnings.

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“Boy.”

Grindelwald’s voice is soft, almost teasing, and Credence looks up in alarm.  He just wants to eat – please, please let him eat.  He’s grateful to be given Graves’ and Grindelwald’s scraps, and his heart beats quickly with fear that Grindelwald has changed his mind about allowing it.

“Yes, sir?” he whispers.  He doesn’t stop eating.  Grindelwald hasn’t taken the food away yet, he’s so hungry –

Grindelwald’s hand falls on the back of his neck, and just like that he goes still.  Grindelwald chuckles.

“Hurry up, pet.”

Credence does, finishing quickly while Grindelwald stands behind him, fingers stroking the side of his neck.  His fingers slip beneath his open collar, brush his cheek – and then twist into his hair, tight and secure and hurting just right.  Credence chokes back a whimper as he feels his cock twitch.

“Aw, pet.  Is there something you want?”

There isn’t – not really.  But it doesn’t matter. Grindelwald wants him to want it, and that may as well be the same thing.

“Yes, sir.  Please – will you touch me? Will you h-hurt me, sir?”

Grindelwald smiles.

“Come along.”

Credence follows the tight grip in his hair to Grindelwald’s bedroom, falling easily onto the bed when Grindelwald shoves him.  He’s shaking.  He doesn’t know what Grindelwald intends to do with him.  It’s always something different, something new, nothing so simple as fucking him.  

He can never prepare for what Grindelwald comes up with.

He tries not to flinch when Grindelwald vanishes his clothes.  He knew it was coming, Grindelwald can have him as he likes, of course he’s naked – he tries not to think about how that was his last shirt, and they won’t give him another.

In one fluid movement Grindelwald is behind him on the bed, grip tight around his throat and pulling him up, back, until he’s leaning against Grindelwald’s chest.  Credence doesn’t flinch away, doesn’t fight, even as he feels Grindelwald’s hot breath on his cheek.  There’s nowhere to go.  Fighting only makes it worse.

The position is new, laying back against Grindelwald like this, but Credence still knows what he wants to hear.

“Will you p-please hurt me now, sir?”

“Hmmm.”  Credence feels Grindelwald smile against his cheek.  “Is that what you want?”

Credence nods, his voice breaking.  “Yes sir, very much.  I love it when you hurt me, I – I love it -”  Tears slip down Credence’s cheeks, and he doesn’t notice them until they splash on his bare chest.

Grindelwald’s hands are on him, twisting and pulling at his nipples, fingernails scraping over his ribs, and then on his cock.  Credence keeps his hips still, perfectly still for Grindelwald as he idly pinches and tugs at the sensitive flesh.  Credence is starting to harden at the attention even as his stomach churns, but that’s normal, that’s natural.

“When was the last time you got to come, pretty thing?”

Credence’s breath catches, and he doesn’t understand.

“Did Percival fuck it out of you?  Did you come from having a cock up your ass?”

Did he?  His life is such a haze of pain, he doesn’t remember.  It hurts when Graves fucks him.  Usually it hurts.  Sometimes when Graves’ cock hits him just right it feels good.  Sometimes the pain feels good.

Slowly, Credence nods.  “Yes sir.”

“When?” Grindelwald breathes.

When?  Credence can’t keep track of the days.  Not today.  Not yesterday.  Not… before that?  He doesn’t know, and panic rises in his throat at what Grindelwald will do to him if he can’t answer the question.

Grindelwald just laughs.  “That long ago?  Or was it just that forgettable?”

“Yes sir,” Credence gasps, praying it’s the right answer though he doesn’t understand what Grindelwald is asking.

“Poor darling,” Grindelwald coos, and Credence shivers.  Grindelwald’s fingers trace their way upwards, slowly, over the rise of his hips and the curve of his side, the ridge of each rib, along the lines of his collarbones until one finger presses under his chin, tipping his head back to rest on Grindelwald’s shoulder.  “I’ll make sure you don’t forget.”

Three of Grindelwald’s fingers press into his mouth while with his other hand he grips his cock, stroking and squeezing, fingers pressing on his tongue as he twitches in Grindelwald’s arms.

It… doesn’t hurt.  There’s a warm pressure in his cock, something rising within him that might be pleasure as Grindelwald moves his hand up and down.

Credence makes a small, uncertain sound in the back of his throat as he suckles Grindelwald’s fingers.

“Hush.  You just get to enjoy it darling, isn’t that nice?”  Grindelwald’s tone is dripping with honey sweetness and Credence doesn’t know what to think.

Once saliva is dripping down Credence’s chin Grindelwald takes his fingers from his mouth, wrapping his spit-slick hand around his shaft and squeezing.  He settles into long, even strokes which have Credence panting, the easy glide slowly working the tension out of his muscles.

There’s no question that it’s pleasure he feels now.  It spreads through him, something warm growing in his belly.  Grindelwald pinches his nipple and his cock twitches, his eyes falling shut.

It might not last, pain could burn away the pleasure at any moment, but right now – right now he lets himself feel it.  He’ll take it while he can, he’ll cling to any last shard of pleasure Grindelwald gives him.

“Does that feel good?  Does your little cock feel good?”

“So good sir, so – oh – ohhh…”

“Are you sure?” Grindelwald asks, and Credence can hear him smirking.  “You asked me to hurt you.”

Credence makes a little noise, a small sound in his throat, and Grindelwald chuckles at his distress even as he tightens his fist around Credence’s cock.

“Don’t fret, doll.  I have other plans today.”

Grindelwald speeds up his strokes, and Credence falls boneless in his arms.  He wants so desperately to feel good – to be allowed, just for a little while, to relax without the fear of pain.  He craves it, he needs it, and Grindelwald holds him so gently that he almost believes he can have it.

“It’s all right my boy,” Grindelwald is murmuring to him.  “It’s all right, let it happen.  You love it.”

He does.  He never thought that Grindelwald could be kind, but this is such a generous gift that Credence finds himself stunned.  His hips rock upwards to meet Grindelwald’s hand, he can’t help it.  The pressure is just right, and when Grindelwald twists his wrist Credence’s breath stutters.

The pleasure washes through him, making him tense and shake and cry out with a little “Ah – ah!”  Before he knows it he’s spilling over Grindelwald’s hand, crying and shaking and utterly gone.

His body buzzes with aftershocks, his head is fuzzy, and Grindelwald presses a kiss to his forehead.  Credence curls in against him, body soft, and Grindelwald pets his hair as he comes down from the soaring pleasure.

“Did you like that?” Grindelwald murmurs.  “Did it make your cock feel good?”

Credence nods, eyes still closed.  “Yes, thank you sir.  Thank you so much, it felt so -”

Credence’s hips jerk when Grindelwald’s fingers fall on him again, oversensitive nerves burning with too much sensation.  Grindelwald’s hand on the back of his neck is all the warning he needs to stay still.  Slowly, deliberately, Grindelwald wraps his hand back around Credence’s shaft.

The pleasure is rough and sharp when he begins to stroke, but Credence can’t deny how good it still feels.  It’s just this side of too much – he’s brimming with sensation, nerves sparking, all of it running right to the core of him.  It touches something inside, something deep.

Credence comes again when Grindelwald rubs his thumb in quick, tight circles over the head of his cock.  The pleasure is such that it dissolves the world, everything going grey until there’s only his heartbeat and the pulsing of his cock.  He can’t believe Grindelwald would give him this.  It’s glorious, overwhelming like pain but good, so unlike everything else in his life that it leaves him reeling.  He never would have thought it possible.  The pale pleasure he salvages for himself by squeezing Graves’ cock while he grinds against the sheets is nothing compared to this.  He wants it to go on forever, this bliss without pain or fear, dizzying ecstasy filling his mind and body.

Words can’t convey his gratitude, but he tries.

“Sir – thank you, it’s incredible sir, it feels so good…”

“I take such good care of you, don’t I boy?” Grindelwald murmurs in his ear, and Credence nods fervently.  Memories of past pain fade before the chance to spend moments feeling human again, and Credence sobs with the relief of it.

“That’s it, ssshh.”  Grindelwald rubs his back and Credence folds into his arms, hiding in the crook of his shoulder as Grindelwald rocks him.  He never thought he’d be treated like this, never thought he’d feel a comforting touch.  He doesn’t know how long it will last, he doesn’t know what it will cost, but he treasures it.  “Hush now, you’re all right.”

He knows he deserves whatever Grindelwald decides to give him, be it pain or pleasure, and he’ll accept it.  When Grindelwald hurts him it’s because that’s his purpose, that’s what he’s for.  Grindelwald has shown him that, and he won’t fight it.

But this pleasure… Credence has the wild, selfish thought that he likes it better.

It scares him to think that way, but if Grindelwald is doing it to him it must be right, he must be allowed to like it.  He likes everything Grindelwald does to him, he has to.

His thoughts fall away when Grindelwald returns to stroking his cock.

“Ah!  S-sir!”

His soft cock is sensitive, tender, almost sore beneath Grindelwald’s palm.  He’s already come twice and he doesn’t know if he can a third time, not so soon.

Grindelwald looks down at him, and he doesn’t stop.  “That’s right, I know you love it.”

Credence shakes, and he struggles not to pull away.  He had loved it.  Now… shouldn’t he still?

With a muttered word from Grindelwald warm slickness drips down his cock, easing the glide and making his skin just barely tingle.  His head falls back with a moan, pleasure outweighing the discomfort again for a moment.  It’s still too much, the sensation overwhelming, rushing through his body as though he’s caught in a loop with nowhere to go.

He squeezes his eyes shut and lets it happen.

When he comes it’s as though the raw sensation is being ripped out of him.  There’s no pleasure, none of the hazy bliss he’d fallen into.  No softness.  Nothing kind in the gentle touch.

Grindelwald gives him no rest, and Credence teeters into pain.  He thrashes his head side to side and he knows how wanton he looks, the lines of his body arching and twisting as though to encourage rather than to protest.  He wouldn’t protest – he knows better.

Tears spill down his cheeks and Grindelwald wipes them away with a tut.

“Why are you crying?  I’m doing this for you.”

Credence chokes on a sob.  He’s wicked, ungrateful, selfish when Grindelwald is only being kind.  He knows better, he should be better.

“Th-thank you sir – Tha – ah – ahh!”

“That’s it.”  Satisfaction curls in Grindelwald’s voice, warm and slow.  “Tell me how much you love it, be a good boy.”

When he finally comes again he screams.  His cock aches and burns as it dribbles thin fluid and Grindelwald just keeps worrying the head, thumb gliding in circles which scorch his core.  His index finger finds Credence’s hole and it’s warm and slick as he crooks it, gently penetrating him.

In the end Grindelwald has to hold him down.  He thrashes, muscles seizing in a desperate attempt to cope.  He’s given up on fighting, he can’t escape, but he can’t stay still.  Grindelwald pins him to the bed, magic binding him, and he cries.

It goes on.  Any thoughts are burned away under the waves of excruciating pleasure, hollowing him out until he feels like an empty husk.  His throat is raw from screaming, cock a throbbing point of pain, and all he knows are Grindelwald’s hands.

When he’s too exhausted to cry Grindelwald leaves him, bored of the game.  Credence lies limp on the bed, his reddened, swollen cock resting against his thigh.  He can’t control his body, limbs twitching and spasming, body wracked with tremors.

He’d loved it.  He knows he did, he’d repeated at over and over and Grindelwald told him so.  This was all for him, a gift, and Grindelwald was so kind.  He likes this better than pain.  This pain was pleasure, right?

Hadn’t it felt good?