Pairing: Demon King! Nightmare Sans x Summoner! Female Reader
Prompt: It's the demons' heat week, and (Y/n) offered to help them out with their urges. What she didn't realize was she'd be helping their enemy, too...
Type: smut
Length: 4.9k words
Background: This was in Her Guardian as part of a spicy week-long bonus thing where each of the guys got a day of the week with Y/n to claim her. The goal of the heat week is procreation (i.e. making babies) and after mating, the heat urges go away. | Takes place on Saturday - the last day of their heat (thus the most intense) and after everyone else's - but it branches off so in this scenario: Dream's never happened and Nightmare's took its place & happened instead
Notes: Lucky Y/n - or unlucky in this case. Them being a demon only changes how tall they are (at/over 6'4"), their power (they're much stronger than humans), and how they see Y/n (among other things I explore in my full-length story that aren't relevant for this smut-shot). I tried to remove any information that pertains to the events of Her Guardian so you can read this as a stand-alone story and understand everything.
SOMETHING TO NOTE: Nightmare is Y/n's enemy so they're on opposing sides and his goal is to kidnap & bring her to the bad guy (his human boss). But I like including nods to His Summoner so his mate is the Y/n of his book (HS), and Dream's Y/n looks just like her/shares her name because obviously they're both you. So if that's confusing: there's two Y/ns that look exactly the same, one was Nightmare's mate and the other is Dream's, and you're the Her Guardian one/Dream's for this smut-shot
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(Y/n) relaxed in the bathtub, running her hands through her (h/c) hair to spread the shampoo through the strands before sinking under the water to wash it out. With every demon satisfied save for the one that claimed he wouldn't give in to his urges because she wasn't his mate, she felt a long soak in the bath was the perfect way to round out the week—even if she would've preferred Dream realized they were made for each other instead of rejecting her. It was getting frustrating to have the truth in bright neon lights yet he continued to close his eyes and pretend he couldn't see it, and she was getting sick of it. She loved him, quite bluntly, but while she could understand his reasons, that didn't make it any easier on her heart. She just wished there was some way to get him to see that what he was looking for was right in front of him.
(Y/n) emerged from the water with a deep sigh, resting her head back on the edge of the tub. A deep chuckle made her head snap up in surprise to see Dream standing beside her, his smirk wide and yellow eyelights gleaming like he was looking at prey. She shivered, trying to hide her unease with a smile. "Hey Dream, what's up?" She pulled some bubbles floating on the surface of the water over to cover her body, his normally positive aura all but missing due to the heat, and it made her shudder as she avoided his gaze.
"I assumed you would be wrapped in an intimate embrace during this week, yet here you are all alone." He adjusted his gloves so they were pulled higher up his arms, each word delivered with a mocking edge. "Do not tell me the others have refused to touch you on some skewed grounds of morality."
She frowned, sitting up in the tub to look him in the eyelights. "I already helped them earlier this week. You didn't hear?"
"I am afraid I did not." He looped his thumbs through his belt, gaze slowly slinking up her body.
She blushed and cleared her throat, hesitantly meeting his eyelights. "Were you coming up here to ask me to help you out?" Her heart beat faster, wondering if she really got him to crack just by waiting until the last day of their heat, and his grin stretched wide.
"As a matter of fact, yes, I would love if you could help me out, angelus." He extended a hand to her and she took it, tilting her head.
"'Angel'?" 'Angelus' was 'angel' in Latin.
His sockets widened but he recovered the next second, letting out a deep chuckle as he pulled her from the water. "Apologies, you simply remind me of Nightmare's mate."
"I remember her being mentioned but I don't know much about her." She stepped onto the bathmat next to the tub, flushing as he slowly dragged his gaze down her body shamelessly. She wasn't sure to what extent the heat affected the demons but she could get used to this confident Dream—especially if it meant he'd finally admit what she already knew. Her heart jumped at the thought as he snatched a towel, wrapping it around her back to pull her towards him so she was flush to his chest.
"Yes, the King lost her many years ago. It is...most lonely at the top, and every reminder of her is agony when you know you will never again lay eyes on her until you yourself expire." He grimaced even as he took his time rubbing the towel over her bare back to dry her. He noticed her sympathetic look and covered his momentary sadness with a wide smirk. "Do not tell me you feel bad for the King of Negativity, (Y/n)."
"I guess I'm just thinking about how if we were to, you know, get together, that would be you someday." His sockets widened as she prattled on, avoiding his unreadable gaze. "And I guess I can understand why you wouldn't want to be with me if you see how badly it affects your brother." It was a painful truth to swallow, but that brief flash of pain across Dream's face said more than enough: Nightmare was tortured every day by losing his mate.
"It is what I get for choosing a human mate," he grumbled, rolling his eyelights, but even his annoyance was seeped in angst.
"I meant it when I said I'd be happy as long as you're happy." She tried to smile but the air was thick with tension, making it waver as he studied her. "I mean, I'm sure Nightmare would find a new mate but I know you're loyal to the end, and if that means you'll only be happy with a demon mate then I really am happy to drop this thing between us."
He didn't react for a moment, then a slow smirk stretched across his teeth. "You are a terrible liar." Her eyes widened as she froze solid. "It eats away at your very soul for Dream to deny you that which you want most of all, and every time he rejects you, you crave him all the more. Pathetic." Her breath caught in her throat as he pulled her more firmly into his chest so she couldn't escape, the glint in his yellow eyelights almost sinister. "The only thing that will get through his thick skull is to see that which he desires but is too blind to see taken from him." He cocked his head, teeth stretching into an impossibly wide smirk. "I truly had no quarrel with you, angelus, but perhaps Dream will realize how much you meant to him in time for the Waylons to end your life in front of him." She scarcely breathed, the hair on the back of her neck standing on end as a dark aura surrounded her, and a tentacle from Dream's back reached towards her and wrapped around her throat as she heard her bedroom door open.
"Summoner?" Dream's voice called from her bedroom.
(Y/n)'s eyes snapped back to 'Dream' as he chuckled darkly. "It seems the ruse is up." He made it sound like nothing more than a game, and he wrapped her up in the towel as he pulled her into his side, arm snug around her waist as he looked out the open window.
"Dream!" Her scream was choked back with the tentacle on her throat. Immediately footsteps led up to the bathroom door and Dream flung it open, sockets barely able to widen in time before 'Dream' focused on a distant shadow and flicked off the light in the bathroom, plunging the room into darkness, and when Dream flipped it back on, both his summoner and the fake were gone.
(Y/n) felt her stomach heave at the feeling of melting into shadow as 'Dream' teleported them both into a dark room. She shoved him away, back slamming into a wall as he did nothing but grin at her and her delicious fear. "[Dream!]" Silence met her mental cry, and she clutched the towel tighter to her body as she pushed herself into the corner of the small room, eyes never leaving the fake Dream. "[What's interrupting our bond? Why can't you hear me??]" Their mental connection had been severed all week, and while she'd assumed it had to do with Dream distancing himself from her physically and mentally, they needed that connection right now! "[Shit, Dream! Why can't you accept we're meant to be? Why did you have to push me away...?]" The thought tapered off into a quiet whimper, her fear and anger nothing but smoke and mirrors. Screaming at him wouldn't fix it—especially when he couldn't hear her anyway.
"Already gave up, human?" Dream's face dissolved into goop, and she watched in horror as Nightmare returned to his normal form, putting his hands in his hoodie pockets as his tentacles batted at the air like the sheer negativity in the cramped space delighted him. "I figured you would put up more of a fight." Each word that slipped from his teeth was soaked in mocking energy and it almost surprised her how evil he could sound without saying anything outright threatening.
"What am I supposed to do?" She huffed, shifting uneasily. "You'd kill me if I tried to escape. I'm boned." The last two words could barely make it past her lips as her gaze fell.
"Dream truly has done a number on you," he mused, leaning closer with amusement twinkling in his lone turquoise eyelight. She bristled, glaring at him as she tried to push herself further into the corner, but with him blocking her only escape and the reminder of what he did to Slash, all she could do was frantically think of some way out of this—surely there had to be some way out of this, right? "I wonder how many lies you feed your aching heart to convince yourself you have any chance with my brother." Nightmare's tentacles curled in amusement as he stepped closer to watch her expression tense with discomfort.
"How do you know so much about us?" Her eyes flickered over his expression in an effort to read him but it seemed both brothers were enigmas.
"Your emotions are laughably easy to read, intentions as transparent as your tears." He cocked his head, smirking. "How many times will you let him drag you down before you learn he will never make you his, angelus?"
She flinched, turning to hide from his cruel smile. "You called your mate 'angelus', didn't you?" The flash of surprise was brief and she barely caught it before he was scowling. "She was your angel?"
"If you are searching for proof my brother will cave, you will find none. I am sure he has told you how dissimilar we are, and my taking a human mate does not change your fate." The words ground out between clenched teeth, and an idea struck her then.
"What was she like?"
"Mea parvus angelus?" He smirked, a tentacle flicking. "My little angel (Y/n)." Her eyes widened with surprise as he continued, leering over her as the shadows seemed to lengthen around him. "She looked just like you, summoner. She-"
"I remind you of her, don't I?" The words were quiet, and despite his displeasure with being interrupted, all he did was snap a tentacle in the air and nod.
"That is hardly an astute observation, human." She ignored the jab, taking only a moment to think of how to use this to her advantage before she sprung her hastily constructed plan.
"Is that why we're in some random undisclosed location instead of your human boss' office?" She used one hand to hold up her towel as the other spread to gesture to the cramped, dark room that felt more like a closet than an actual room. "I mean, you're instructed to bring me to them, aren't you? It would be in your best interest to bring me straight to them, yet we're here."
"If you are hoping I am violating my contract, you will be sorely disappointed." He smirked, hands relaxing in his pockets. "They are not aware you are here, and if they do not know, they cannot give me any such instruction to violate."
She frowned, but the next second she was smiling. "Which means you didn't want them to know you were sneaking into my house to kidnap me." A tentacle flicked, but when he said nothing, she tilted her head. "Why?"
"I forget you are not nearly so dense," he grumbled, teeth curved into a scowl.
"If you always had a way into my house, why now?" Her questions made his socket twitch, but the next thing she said made it widen in a panic. "Is it because it's your heat week?"
"I do not have to explain myself to a human!" he spat, tentacles writhing with anger on his back, and he stepped towards her so his chest was flush to hers, pushing her back into the corner as she offered a shaky smile.
"I'm willing to help if that's why I'm here." She actually stunned him into silence, and at such blatant loss of words, her smile turned more confident. "I mean, assuming I'm right about your intentions, I'll help if you bring me back home afterwards."
His surprise fell away to distaste but he didn't back up. "You think helping me will prevent your demise?"
"I think you're lonely." It was subtle but she felt him stiffen against her. "You said it's lonely at the top, and maybe seeing a girl that looks just like your long lost mate makes that loneliness impossible to ignore. You miss her, and even if I'm not her, just for today you want to pretend I'm her so you can remember what happiness felt like."
Nightmare's eyelight darted to the side as he tsk'd. "I am perfectly happy without her."
"But you gave your soul to her, didn't you? You soul bonded?" He stayed silent and (Y/n) gently reached out to touch him. "A piece of your soul is missing because she's gone-" He snatched her wrist with a tentacle, making her freeze as his eyelight returned to her, something unreadable on his face.
"Do not assume to know me, human." She shivered at the sheer fury in his tone.
"It's scary being known, isn't it?" He grit his teeth as her smile appeared much too sweet to be pointed at him. "But I'm just speculating. If I'm so wrong, why not educate the stupid human?" She tugged at his impossibly strong grip but he refused to release her wrist.
"You are attempting to goad me into giving you information. It will not work." His composure was back as he leaned down so she was forced to look up into his face to maintain eye contact.
"If it's as bad to lose your mate as you make it sound, I get why Dream turned me down—especially if he sees how it affects you."
"He is a pathetic fool for pushing you away." He turned her wrist over so her palm was up, and gently he pulled her hand up so it was resting against his cheekbone. "He is wasting time by being stubborn and he will regret it if he does not die before then." He sounded like he was speaking from experience and she tilted her head curiously. The King released a deep sigh, some of the perpetual anger on his face melting away as he looked at her. There was an almost warm feel to his gaze that made her cheeks redden, and he released a deep chuckle. "You are so much like her..." A tentacle stroked her cheek tenderly—something she never thought he'd be capable of—and she smiled almost on instinct.
"So I was onto something, wasn't I?" He frowned, his teeth lifting in subtle disgust, but he offered a curt nod. It was like he didn't want to be open and honest, but because she was so similar to the mate he devoted his soul to, the words came out almost unwittingly. She rose her other hand to mirror the one against his cheek, feeling him stiffen with surprise as her familiar (e/c) eyes gazed up at him with that near identical soft look he knew so well. "You can't bring me to your boss—or at least you don't want to. You can't watch your lover die twice."
"I would much sooner die than relive it." He dipped his head in quiet acknowledgement.
"So bring me home." She admittedly sounded like she was begging, but when he didn't react, she sighed. "Why am I really here?"
"The only way this conflict resolves is by your demise or my own." Each word was delivered evenly like the gravity of his words didn't weigh on him, but she felt each syllable sink into her chest and make it hard to breathe. There was an undeniable bond between them that rivaled her own bond with her demons, whether it was due to her closeness with his brother or because they were lovers in another timeline, she couldn't say.
"Surely there has to be another way?" (Y/n) couldn't explain the sadness that enveloped her at the thought of Nightmare dying, and she swore she saw the flash of a genuine smile cross his face.
"Just like her," she heard him whisper under his breath, then his hand grabbed her chin, tilting her head up so her lips almost brushed his teeth. "Death is not a fate you can outrun, angelus." His eyelight glazed over with a memory as he added, "All you can do is postpone it." She didn't expect to feel sorry for him, and she wondered if it was his aura that was making her feel comfortable around him before remembering he embodied negativity; if anything, she should be hating him all the more because of it, but the air between them was more than friendly. The only explanation she could conjure up was she reminded him so vividly of his lover that he wanted her to be comfortable in his presence just like his angelus used to. And she was, as crazy as that sounded.
"Where is your fear, (Y/n)?" A tentacle slid up her side as another stroked her cheek, and Nightmare held her chin more firmly as he leaned closer so she could feel his breath fan against her lips. He pinned her body to the wall with his, one arm propped against it, and he could feel every bit of her through the towel.
"You're not very scary when you're looking at me like that." He frowned, but before he could reply, (Y/n) smiled warmly. "I prefer it."
"And tell me, how am I looking at you?" He cocked his head to the side, eyelight glowing all the brighter as he slid one of his legs between hers so his knee brushed against her pussy. Her heart skipped, her face flushing as his gaze ran over her flustered reaction, and he let out a chuckle that reverberated in his chest. "You are so much like her."
"Does that mean you'll bring me home since you know what'll happen if you bring me to your boss?" Her smile had obvious hope, and despite his distaste for the positivity, he did nothing but scoff.
"So I can watch my brother fumble his chance with you instead of taking you as he should?" He almost sounded disgusted with Dream, and she cracked a smile as his thumb brushed her bottom lip. "I would not be so slow to claim what is mine."
"You almost sound like you want to sleep with me just to spite him," she laughed, but when he only smirked, her eyes widened and her lips parted with surprise.
"You are not his mate, summoner, and perhaps by setting an example, that jealousy that seizes his very soul from my claiming you will spur him into action." Nothing like his brother taking his girl to get him to finally confess and stop running her around in circles. But even as he tried to pretend he only wanted to one-up Dream, she knew his motivation wasn't nearly so shallow.
Nightmare abruptly wrapped his hands around her thighs, pulling her up so her legs could wrap around his hips, and (Y/n) gasped. "But aren't you cheating on your mate?" He stopped to smile at her, tentacles sliding up her sides and under the towel as her face burned crimson.
"My commitment to her is complete, and though I will never take another mate in my lifetime, you are correct in assuming I am more lenient on who I relieve my heat urges with." He trailed skeleton kisses down her neck that made a shiver travel up her spine, and she clung to his hoodie as he pushed her more firmly into the wall.
"And this has nothing to do with me looking just like her?" she asked breathlessly.
He paused to look back at her, his smirk an attempt at hiding the deep sadness in his eyelight that hadn't left him since he lost his mate. "You are her, angelus." Her breath caught, and he leaned closer to kiss her sweetly. It held years of pent up feelings, and while she couldn't feel his emotions like he could feel hers, she understood just what he meant. He'd never be with his lover again, but for just that one moment, he saw angelus in her, and as sappy as it was, he wanted to be with his summoner one last time.
"Are you sure we can do this here?" (Y/n) whispered, glancing towards the door out of the room, and he smirked.
"We are far away from prying ears. You can be as loud as you want~" She flushed as he grinded his hips into her so she could feel him, and he trailed skeleton kisses down her jaw, sinking his teeth into the base of her neck and pulling a gasp from her lips. His turquoise tongue ran over the mark before he bit on a spot just above it, sucking on it as she shivered. His tentacles curled around her towel to pull it from her body, dropping it behind him as two of them explored her body. They caressed her chest, lightly squeezing her breasts as the tips brushed her nipples, and she arched her back into his touch with a quiet moan.
"Be loud for me, angelus~" he purred against her skin, his tongue hot along her neck as his eyelight took in her flustered expression. She obeyed, feeling his fingers dig into her thighs enough to leave marks as he grinded against her but not caring, focusing only on whimpering loud enough she was sure someone would hear them. "Mmm, good girl~" Her hands clenched his hoodie tighter as she rested her forehead against his. "You think you're ready for me?" His eyelight ran over her face as she nodded, smiling breathlessly, and he chuckled. "Always so obedient~" He pressed his teeth to her lips as he used a hand to push his shorts down, guiding his cock to her entrance and slowly pushing himself inside of her. She gasped, clinging to him tightly, and he adjusted his grip on her thighs as a tentacle pet her head.
"Shit, you're big," she whispered, legs tightening almost involuntarily around his hips.
"I am a King, summoner." She could hear his smirk without seeing it, and she avoided his intense gaze as he gently pulled most of the way out of her before pushing himself fully back in. She released another gasp that he muffled with a kiss, tentacles exploring her body and massaging her skin to ease her discomfort.
He rocked his hips, smoothly sliding in and out of her as she whimpered, "Ngh~ King~"
He chuckled, fucking her faster just to hear her adorably pathetic moans. "Who is doing this to you, summoner?" It would've come off as mocking if he didn't sound pleased at her utterly unraveling from what he was doing to her.
"Night- Nightmare~" She couldn't think with his tentacles all over her, and he seemed to note this as he tilted his head at her with a wide smirk.
"That's my girl~" He held one of her legs higher to hit a deeper spot inside her, making her gasp. "Let everyone know who is pleasing you like this~" She wondered for a moment how Dream would react if he heard her thoughts right then, dissolving to pieces under Nightmare as he pounded her against the wall, but even as she knew their connection was still severed, part of her sided with Nightmare as she hoped this would finally be the push Dream needed to admit his feelings.
Nightmare adjusted his grip to push her higher up the wall, tentacles caressing her whole body as he panted heavily, his teeth by her ear so she heard his every deep groan. It sent a shiver up her spine and she whimpered, producing a low chuckle from the Demon King. "You are taking me so well, summoner. I think it is time I change that~" The next second he was slamming her back into the wall with every thrust, making her gasp and whimper as she clung to him tightly. His power left her breathless, all of those pent up emotions over losing his angelus and being forced to work for a human he despised coming out as he fucked her up, and she could do nothing but moan from all he was doing to her.
"Fuck, Nightmare~" And even as she moaned her enemy's name, she couldn't find it in her to care. He wasn't wasting time like his brother, claiming her with the swiftness Dream lacked, and it made her core tighten. He was a powerful King, and while before that had made her nervous, now it thrilled her in a good way.
"You make such beautiful sounds, summoner~" Nightmare teased, pants only getting heavier as his grip on her thighs tightened. His sweet dirty talk made a blush rise to her cheeks, and she gasped as he rammed his dick against her g spot. Her moans rose in pitch and he chuckled as she tilted her head back, giving him access to bite and suckle the same spot at the base of her neck.
It wasn't long before she gasped out a pathetic whimper, unable to warn him before she tipped over that edge and her orgasm sent waves of pleasure rolling throughout her body. Her pussy squeezed around his thick cock and he grunted, slamming her back into the wall as he pumped in and out of her to ride out her high before finally slamming his hips into her and stilling, shooting his hot sticky cum deep inside her with a quiet groan.
Nightmare set (Y/n) back on her feet, offering her the towel with one of his tentacles. She wrapped it around herself with shaking legs, using a corner to wipe the cum dripping down her thigh, and he curled a tentacle around her waist to keep her upright as he put his hands in his pockets. There was a fresh softness to his gaze as he looked at her like he saw angelus in her place, lying to himself that (Y/n) was the mate he lost so long ago. But even if he did, he didn't act like it, briskly moving on with a, "I believe it is time you return home."
"You're actually bringing me back?" Her eyes widened and he scoffed.
"Is that not what you wanted? To return to my pitiful brother?"
"Well..." She held a hand over the mark on her neck, knowing full well he could feel her embarrassment.
He chuckled, a tentacle flicking her cheek. "A gift to help him see what he is missing."
"Why are you helping me?" She looked up at him with big doe eyes that he lost himself in. "You hate Dream and you have to kill me." Her confusion was palpable but he simply stroked her cheek with a tentacle.
"Our heat is very powerful, summoner. I was simply using you, nothing more." Even in his effort to sound detached there was a note of genuine warmth he couldn't shake. "I am taking you before he has the chance so as to get under his skin, and you are granted another day to live by helping me." It sounded like a clear-cut business transaction, but that feeling in the air between them told her it was more than that. But she knew he wouldn't ever admit it, especially not when the heat wasn't driving him crazy, so instead she offered a smile.
"Thanks for showing me a good time, Nightmare."
Her light tone amused him, and he smirked down at her. "A Queen deserves to be taken by a King." He offered her a tentacle. "Now, let us return you home." He was much too happy about pouncing on the opportunity before Dream but she couldn't exactly fault him for taking advantage of the hole Dream left—especially when she herself was so willing.
(Y/n) took Nightmare's tentacle and he spun her into his arms, making her gasp with surprise. "Would you like me to take you to bed?" Her face went scarlet and he smirked. "By bringing you to your bedroom, summoner." She ducked her head with embarrassment as she put the forcefield down in her bedroom so he could teleport her home.
"Right, sorry Noche."
He paused, something akin to pain breaking his expression. "What?"
"I said 'sorry Noctis'." She tilted her head in confusion as he frowned, turning away from her as he teleported them both back to her home. He put on a smirk in preparation for his confrontation with Dream about stealing his girl away, all the while feeling her curious gaze on him—his curious little summoner. And even if he knew deep down this wasn't his (Y/n), it still put his soul at ease to be with her one last time.