Word Count: ~2,150
Content/Warnings: established relationship, knotting, anal sex, (too) brief rimming, dirty talk, bottom!harry
Summary: Draco has a potions accident at work that results in some interesting side effects.
Notes: lq_traintracks, I really wanted to write something for you, because you have always been so incredibly lovely, and you wrote me such a fabulous fic for my birthday last year. I've been wanting to try my hand at knotting!fic, so when I saw knotting on your list of likes, it was like the stars aligned. I really hope you enjoy this and I hope you have a fabulous birthday. <3
Thanks to capitu, lauren3210, and dicta_contrion for looking this over for me! I played around with it a bit since, so all remaining mistakes are my own.
50 Reasons to Have Sex Masterlist
Read on AO3
Harry paced in front of the Floo anxiously, his eyes flicking to the empty grate every few seconds. He paused, about to cast another Tempus—something he'd been doing every other minute since he got Draco's owl—when the fireplace flared green, and Draco walked calmly into the living room.
"Fuck, Draco!" Harry exclaimed, pulling him into a hug before carefully inspecting him. "Are you okay?"
"Yes, I'm fine. Like I told you, it was just a little potions accident."
Harry narrowed his eyes. "Just a little potions accident? The last time that happened you were in St Mungo's for a week!" Harry took a deep breath. "Are you sure you're okay?"
"Yes," Draco replied quickly, before wincing slightly. "Mostly." He held up a hand to hold off Harry's indignant response. "There are just a few...side effects."
"What side effects?" Harry asked warily
"Williams has been working on a potion that...well, nobody actually told me what it's supposed to do, but they've been studying heat cycles in wolves, trying to emulate certain attributes."
"And, of course, Williams had to go and spill the whole vial all over me, while the potion's still in testing. I think that they're trying to create something to increase sex drive, though apparently it's been having slightly different effects. I've been assured it should wear off in less than a week, but until then..." He trailed off, refusing to meet Harry's eyes.
"Dammit Draco, just tell me what the hell is the matter with you!" Harry yelled, his heart racing as he imagined all the horrible things that might be wrong with Draco.
"I've got a knot."
Harry paused. Blinked. "What?"
"A knot," Draco said dryly, as if his cheeks weren't dusted pink. "On my prick."
"Um…" Harry looked at Draco with concern, wondering if maybe the side effect was mental rather than physical, because Draco kept talking about knots like that was supposed to have some kind of meaning to Harry.
"Oh, honestly!" Draco sighed loudly, rubbing at the bridge of his nose. "When canines have sex, the base of the male's penis expands inside the female, tying them together. It's called a knot. Which is what I have," Draco explained, hands twitching towards his groin as if to cover himself.
"Really? Right now?" Harry's stomach felt fluttery at the thought, and he couldn't contain his curiosity. "How big is it?"
Draco bit his lip. "Well, not right now. It starts to form with pressure and fully expands when I'm about to come." He looked down, his brow furrowed in thought. "It's about the size of a fist."
"How do you know?" Harry asked, his hands trailing carefully down Draco's chest of their own accord.
"Well I had to wank off in the lab, didn't I." Draco shuddered. "It was horrible. But they needed to verify the effects. So I had to go into my office and get myself off." He paused, sharp eyes taking in Harry and his wandering hands. A sly smile spread across his face. "Thankfully it didn't take too long. I just had to imagine all those delicious noises you made last week when I fucked you over the sofa."
Harry swallowed, his cock stiffening up at Draco's words and the memory of that particularly enthusiastic shag. He slipped his hand to the front of Draco's trousers and massaged the growing bulge, thinking about Draco's side effect.
Harry had never been ashamed of the fact that he enjoyed bottoming. He didn't see the point in being embarrassed by something that he loved. And he really loved being fucked. Loved the freedom of it, the intimacy, loved the stretch and the burn, loved the all-encompassing feeling of being so full. Sometimes, when Draco was fucking him good and hard, he thought about what it would be like to take more. Last week, during the sofa shag, Draco had been so worked up tracing Harry's rim, where it was stretched wide around Draco prick, that he'd slipped in a lube-slick finger alongside his cock. Harry had never come so hard in his life. He'd been waiting for a good opportunity to talk about it with Draco, but it seemed like fortune had spilled a rather serendipitous potion all over Draco's lap.
"We should—" Harry cleared his throat, cheeks hot. "We should try it out."
Draco's eyes dilated as he absorbed Harry's words. "You want me to knot you?" He asked, carefully enunciating each word as his eyes stayed intent on Harry's.
Harry's entire body flushed with heat at the thought, at the idea of being so full of Draco that they couldn't be parted. "Fuck, yes," he moaned.
Draco was on him in a flash, his mouth hard and desperate against Harry's as frantic hands worked the buttons of his shirt. Harry laughed as Draco started trailing kisses across his cheek and down his throat, licking his Adam's apple before sucking on the skin right below his jaw.
"You like that, don't you?" Harry asked breathlessly. "You like the thought of fucking me open, of seeing me stretched wide around your knot. Keeping me plugged full of your come."
Draco let out a high pitched keen, and began pushing them insistently towards the bedroom. Harry grinned
He'd learned early on in their relationship that dirty talk got Draco going like nothing else. It had been a bit difficult, at first, for Harry to voice all the filthy things that he was thinking, but the rewards had been more than worth it; now Harry was barely even blushing as he talked about Draco knotting him.
After several long minutes, they finally reached the bedroom. Draco had been seemingly unable to pass a flat surface without pressing Harry up against it and kissing him breathless, and Harry was eager to divest them of as many articles of clothing as possible. They reached their bedroom panting and naked, a haphazard trail of discarded clothing in their wake.
"Hands and knees on the bed," Draco growled, kissing Harry hard on the mouth before walking over to grab the lube. Harry quickly scrambled into position, feeling like he would vibrate right out of his skin with anticipation.
Draco crawled up onto the bed behind Harry and spanked Harry's bum lightly before his hands grabbed Harry’s cheeks, pulling them apart and exposing his furled hole. Harry looked over his shoulder, eyelids fluttering as Draco leaned down and gave a slow, filthy lick across his entrance.
"Fuck, Harry," Draco murmured, voice low. "Wish I could just open you up on my tongue. But I think you'll need more than that if you're going to take my knot."
Harry shivered at the reminder, and at the cool sensation of lube being dripped directly onto his hole. Draco pushed two fingers in without fanfare, fucking roughly inside of Harry, his fingers pressing firmly against his inner walls. Harry pressed back into the raw sensation, undulating his hips until Draco added a third finger, pushing even more lube inside of him, scissoring his fingers with each outward motion. Fuck, he felt so wet, lube dripping out of his hole and down his balls, Draco's fingers pressing in and out of him with loud, filthy sucking sounds.
"Oh, fuck me," Harry whined, desperate for more. "I'm ready."
"You sure?" Draco asked as he twisted his fingers, brushing against Harry's prostate and making his legs shake with the pleasure of it. "You think you can take my knot?"
Draco slowly pulled out his fingers, and Harry bit his lip on a whimper at the feeling of loss. Luckily he didn't have to wait long, because just a moment later Harry felt the slick, spongy head of Draco's cock brushing teasingly over his entrance. Harry relaxed and pushed back, sighing in relief when Draco pushed forward and his cock sank inside, inch by pleasurable inch.
Harry hummed when Draco was fully seated, clenching down on the hard length inside of him and relishing the indescribable rush of feeling. Draco's hands trailed up his flanks, kneading the fleshy globes of his arse before gripping his hips, holding him still as he slowly pulled out before slamming back in, hard.
Harry gasped and collapsed onto his elbows, hands fisting in the sheets to brace himself against Draco's unforgiving rhythm. Little choked-out noises escaped Harry's throat, fucked out of him by the force of Draco's thrusts. His cock was rock hard, slapping up against his stomach and leaking precome onto the sheets below him. Draco rutted into him with single-minded enthusiasm, tilting Harry's hips just slightly so that his cock brushed up against Harry's prostate, making Harry's vision blur and his ears ring.
Sex with Draco was always mind-blowing and intense, but this was something more. He'd never felt so desperate for it, so out of control with desire. Things got rough sometimes, sure, but Harry hadn't ever seen Draco so lust-crazed, like he would die if he wasn't fucking Harry into the mattress. The animalistic rutting made Harry’s blood burn, made something fierce and feral rise up in him, begging to be claimed.
The pace picked up, and Harry would’ve sworn that Draco's cock was getting bigger, before it hit him that it was, that he was feeling Draco's knot forming. He wanted it with a primal savagery that shocked him in it's intensity.
"Fuck, Harry," Draco panted, as he continued to fuck relentlessly into Harry. The knot was starting to catch on Harry's rim with each outward pull, and Harry knew that soon it would be too big to pull out. "I'm going to come, are you sure you want this?"
"Yes." Harry arched his back, putting himself even more prominently on display. "Give it to me," he commanded in a low growl, his desperation making him greedy.
Draco let out a low rumbling sound and his grip on Harry's hips tightened as he fucked in one final time, before shouting out his orgasm. Harry gasped as Draco's expanding knot filled him up. The pressure was intense, building and building until Harry almost thought it would be too much, that he wouldn't be able to take it. But finally it stopped, and Draco's cock locked firmly inside him. Draco was still shuddering through his climax above Harry, his hands trembling on Harry's hips. Harry focused on his breathing, relaxing his muscles before shifting slightly, shouting aloud as the firm flesh rubbed up against his prostate, reminding him that he was still very hard.
At Harry's shout, Draco seemed to come back to himself, his hands sweeping up and down Harry's back before he began thrusting his hips. He ground his knot into Harry, pressing hard against the sensitive bundle of nerves that had Harry seeing stars. Harry spasmed at the concentrated pleasure, whimpering as Draco circled his hips filthily into his own. He'd never in his life felt so completely owned and wanted. Like Draco's knot in his arse was some kind of brand, a primitive mark claiming Harry as his. Draco slid a hand underneath Harry's chest, pressing in as he pinched one of Harry's sensitive nipples, and that was all it took, Harry was coming, gasping wide-eyed into his pillow as his cock spurted untouched.
"Fuck," Draco moaned, as Harry clamped down uncontrollably on his knot.
Harry's bones felt liquid as he collapsed onto the bed, every bit of pleasure completely wrung from his body. There was a twinge in his arse, reminding him that Draco was still large inside of him, and he looked over his shoulder at Draco's disheveled face.
"So, how long does this last for?" He asked with a lazy grin.
"Don't you think that's something you should have asked before I fucked you?" Draco chuckled, but he hesitated before continuing, "Anywhere from ten minutes to an hour."
"Hmm, that's the idea," Draco murmured, kissing Harry's shoulder blade. "Here, why don't we lay on our sides, it'll be more comfortable that way."
They carefully arranged themselves on their sides, Draco plastered all along Harry's back, every inch of their skin fused together.
Harry breathed deeply. He felt warm and sleepy and surprisingly relaxed considering he had a knot in his arse. Actually, it felt pretty incredible filling him up, and the thought of being kept full of Draco's come was wonderfully erotic.
"How long until the potion wears off, again?"
Draco hummed, fingers playing idly with the strands of Harry's hair. "No longer than a week. Why?"
"Because we should definitely do this again." Harry wriggled his bum enticingly, clenching down slightly on the swollen knot.
Draco hissed at the sensation before leaning in and blowing hotly against Harry's ear. "Again?" Draco purred, grinding his hips into Harry's arse, stimulating Harry's sensitive nerve-endings. "We're not even finished with round one."