Horror wasn't sure how he got into this mess. Suspended in the air naked by Nightmare's tentacles while being groped by him in front of his au's monsters.
It started this morning during breakfast. Horror was minding his own business in the kitchen of Nightmare's hangout when said skeleton bursts in demanding Horror to follow him in his au. Apparently Nightmare needed some item from his au that is in the hands of another. Nightmare refused to answer his question when he asked and he knew better than to pry. Horror had no choice as he was grabbed by the black tentacles and dragged through a portal.
They met the monsters in his dust covered Snowdin as it was the only place Queen Undyne never visits. Said monsters were Madjick and NightNight.
"Alright, where is the key?" Nightmare demanded while Horror stood behind him looking bored. This was his domain so he wasn't afraid. Plus Nightmare is strong and can take care of himself.
"We have it. But do you have what we want?" Madjick said with a bloodthirsty grin.
Nightmare rolled his eye and with a tentacle pulled out a bag and tossed it at them. NightNight inspect the bag and pulled out a cinnamon bunny. Horror realized that they must have bargained for food. His au was on rations and food is a rarity. He was lucky he joined up with Nightmare. Now he doesn't have to scavenge for food for himself or his brother.
"There. Now, they key." Nightmare demanded.
"You mean this?" Madjick said pulling out a shiny golden key with a blue star shaped gem at the end. "Hmmm...Yeah no sorry." he said with a grin.
"What?!" Nightmare roared but the two didn't even flinch.
"It took us weeks to find this shiny thing and food is not enough to satisfy our hunger." Madjick stated and hovered the key with his magic. "And you seem to need it desperately. So.... How about we make a deal?"
"How about I kill you both and get the key from your dust!"
Madjick laughed in glee. "Nice try. But you can't do that here. So, do you want to hear the deal?"
Nightmare growled, his tentacles moving around agitated. Finally he sighed. "Fine."
"Great great!" Madjick cheered before clearing his throat. "We want a show."
"What?" both Nightmare and Horror voiced out.
"See, we don't get shows here anymore. What with everyone out to kill each other. And I'm feeling a bit horny." Madjick stated and Nightmare made a disgusted face.
"I'm not stripping." Nightmare stated firmly while crossing his arms and Madjick laughed.
"Silly monster! I do not want you! I want him." he pointed at Horror who stared wide eyed.
"What?!" he yelled in fury and embarrassment.
"You have been a pain in my tail ever since you came in Snowdin. Walking around like you owned the place and stealing any food we come across. It'd be such a fulfilling sight to see you in a situation." Madjick said lustfully and Horror backed away looking flustered and angered at the same time.
"Hell no!" Horror yelled, his hand twitching to grab his axe but he left it back at the hangout.
"Do you want the key or not?" the monster asked showing off the shiny object just out of reach.
"No way! This ain't worth it! C'mon Nightma-!" Horror began walking away when black tentacles grabbed his wrists and legs and pulled him back.
"Nightmare!" Horror yelped in surprise as he was suspended in mid air, his feet an inc of the snow covered ground. His wrist held above his head and his legs spread slightly. He couldn't move an inch as he was forcefully exposed in front of the two monsters. "What are you doing?!"
"Sorry Horror." Nightmare said, his voice devoid of emotion as his tentacles held the other in place. "But I need that key."
Ignoring the look of betrayal from the skeleton, Madjick bounced happily in the air. "Good good! Now, give us a good show and we'll give you the key."
All at once, more tentacles began moving over Horror's body moving from his ribs to his spine. The action made Horror bite back a groan, his face felt hot with a red blush. Going under his shirt, Nightmare rubbed and trailed his ribs and spine in slow teasing motions seding sparks of electricity through the other.
"a-ahn..." Horror groaned and gasped when he felt a tentacle on his spine, coil around the sensitive bones and jerked him off.
His body shook and shiver under the stimulation and he suppressed a whine when a tentacle moved to the front of his shorts and roughly groped his crotch. His traitorus body reacted to Nightmare's touch and red magic pooled at his pelvis making it glow. He couldn't deny that it felt good and almost made him want to close his eyes and submit.
"Good good! Now we want to see his bones!" Madjick demanded making Horror jerk in his bonds in fear and embarrassment at the reminder of his audience. But his struggles were in vain when Nightmare ripped his shirt open revealing his ivory ribs marred with scars.
He had the urge to curl up to hide himself but the binds held fast and he could only writhe around in pleasure as Nightmare stimulated him. The tentacles felt icy cold on his ribs yet it made his bones burn with desire. Especially when two of them began trailing up his femur teasingly.
He had been fighting back making any noise other than gasps and groans but when a single tentacle trailed over a scar on his spine, he arched back with a moan.
"Oh a sweet spot eh?" Nightmare grinned, arching his brow. "Wonder what happens when I do this?"
Horror screamed in pleasure when he pressed harder on that spot, sending a spark of white hot pleasure down his spine, his magic finally taking shape under his shorts with an audible crack. The tentacle on his crotch stopped for a moment and rubbed harder feeling the tight hole and wetness beneath his shorts.
Horror whined and tried to hide his flushed face in his arms. It was embarrassing. Him, the murderous Sans, exposed so lewdly in front of two of his au monsters being groped by Nightmare. It didn't help when his hips bucked into the tentacle unconsciously searching for any stimulation despite his brain's orders. He felt embarrassed tears dot the corners of his eyes.
The monsters however enjoyed what they were seeing. "Very nice! How about we see that cute little flower?"
Nightmare in response began wrapping the tentacle on his crotch around his pelvis, covering it as two more began pulling down his shorts teasingly. The shorts fell to the ground and into the snow yet the tentacle around his pelvis obscured the view of his summoned pussy from view.
Horror opened one eye to stare at Nightmare, feeling confused. Didn't Nightmare want the two to see him? Didn't he want to see the other embarrassed? He felt a tentacle on the back of his skull, not stimulating but just resting there. Like a reassurance. It only made him more confused but it felt nice.
"Hey! What gives?" Madjick yelled at Nightmare who stared him down unblinking.
"Did you honestly think I'd let you see him?" he growled lowly and possesively. "I said I'd give you a show. I never said that you could see his pussy. He is mine."
The tentacles tightened possessively and continued their work twice as hard drawing out more lewd noises from the others mouth.
"Horror came to me. He signed himself up to me. Therefore he is mine. And only I get to see him in all his lewd glory." Nightmare growled and at the same time made one tentacle hover under Horror between his opened legs. Clearly making sure the other two see it.
"Everything he is belongs to me. From his body and mind. From his lewd sounds and soul. All mine. And I'm not keen on sharing."
The tentacle shot up and trailed over the lips of his pussy making the other moan and buck his hips. It was teasing, slowly dragging the tip around his wet leaking hole, making the insides clench in anticipation before moving up to rub firmly on the bundle of nerves on top. Horror moaned loudly and spread his legs wider. He has never been touched in such a way, only ever being the dom and is incredibly sensitive. And he knew Nightmare would take that to his advantage. To the others, all they could see is a tentacle writhing between Horror's legs making him moan aloud but it only make the scene more arousing.
"While I may agree to give you a show, you are not allowed to see his pussy. So all you can do is watch and hear as I take him and make him writhe and come under me." Nightmare smirked at their flustered face.
With his words Nightmare breached the tight hole with the tentacle making stars dance in Horror's eyes. Pleasure curled up his spine as Nightmare made it move in and out slowly almost teasingly. It went on for a while, making sure Horror got used to the feeling before getting rougher with its thrusts. Horror swore he felt it grow larger but he didn't have time to think about it as it delve in and out roughly.
"Ahh...Ngh ah... N-night....mare..." Horror breathed out with a groan, closing his eyes and titled his head back. His plea made the other two blush in their frozen state and Nightmare's smirk grew.
"You see? He loves it with me. You're lucky you get to see this at all. He is quite a sight." It was then that Nightmare hit something inside of Horror that made him scream and clench on the tentacle.
"Nightmare! Aaah! Please! Please make me come!" Horror begged and screamed louder when Nightmare hit his sweet spot directly with each thrust. One tentacle moved from his ribs downwards towards his pelvis and circled his clit. The added stimulation made him see stars and it didn't take long for him to come with a loud scream. Red juices exploded around the tentacle and drip down his legs and onto the snow staining it pink.
Nightmare relished in Horror's screams of pleasure and his smirk widened when he heard the other come. He didn't stop thrusting making the other moan as his orgasm was prolonged. When Nightmare felt the other go limp in his grasp did he remove the tentacle and showed it off to Madjick and NightNight. The tip covered in red translucent cum which he sucked it off with a groan and a lewd pop. He directed his gaze towards the two frozen monsters.
"Now, I believe I fulfilled your request. Now hand me the key."Nightmare demanded with no room for argument and Madjick threw him the key. Nightmare caught it and kept it in his pockets.
"Nice doing business with you! Now we are taking our lea-."
Madjick was cut off by the others laughter. "I'm sorry. If you think I'm going to let you ho after what you just saw, then buddy you are dead wrong."
Both monsters backed away in fear when Nightmare reared the tentacles that are not holding a panting and twitching Horror. The black tendrils looking more like sharp blades coming out of the others back.
"H-hey friend! Let's not get hasty-!"
Without letting the other finish his sentence, Nightmare pierced the others Soul with his blade like tendrils turning the other to dust and instantly doing it to NightNight. The area is now silent except for Horror's panting.
With a content sigh Nightmare turned around to face Horror who is still suspended and twitching with after shocks, still in his orgasm induced high. Gently, he sat Horror down on a large tentacle and removed the ones holding his wrists, legs and the one covering his pelvis. His pussy already disappeared. The tentacle supported the other's back as he came down from his high. Nightmare pulled the other closer and rasped his knuckles over the others skull who leaned into his touch.
Moments later, Horror's eye focused and he gave a grin. "That was...amazing."
Nightmare rolled his eyes and grabbed the others shorts from the ground. Using his tentacles and ignoring the yelp of surprise he lifted Horror's pelvis and pulled the shorts back on.
"Damn, I thought you would.... You would...." Horror trailed off looking to the side with a blush.
"What? That I'd let those savages see you vulnerable without dusting them?" Nightmare arched a brow. "Please, I take care of my boys. I was planning on dusting them the moment he went back on his deal."
"So why didn't you?" Horror asked with narrowed eyes and Nightmare grinned.
"I wanted an excuse to wreak you." Ignoring the other sputter and blush, Nightmare wrapped Horror's torso with his tentacles and held him as he crossed the portal. Horror didn't complain as he yawned tiredly and fell asleep in Nightmare's hold.
That night, Nightmare tucked the other in his bed and left without a word.