The Beast Within

by LoneUnicornWriter

Rating: mature
Tags: Sex, Anthro, Slice of Life, My Little Pony: Friendship is Magic, Alternate Universe, Romance, Spike, Rarity
Length: 3910

Spike follows Rarity into the forest only to meet with her "dark" side

Ever since Rarity's transformation, she's been disappearing from Ponyville every month, and when she returns she refuses to tell anyone where she's been. One night Spike follows her and ends up at the the Castle of the two Royal Sisters, there he sees her transform into her Nightmare form.

At first Spike believes that she's trying to take over Equestria again, but Rarity explains that despite her friends freeing her, a small amount of the dark magic that influenced her remained, and once every month she is forcefully transformed. As a result, she flees to the castle to keep herself in check so that she doesn't become a danger to anyone.

While Spike tries to comfort her and tells her that he'll be there for her even if she hurt's him, Rarity reveals that she isn't trying to hold back her violent side...but rather her lustful side, a part of her that has gotten stronger every night, and a males presence simply makes that lust stronger...

Art done by Dan-Fortesque

Edited by Ernest Wood

Fetish Trigger Warning: Light Bondage, Cum Inflation, Butt Expansion, and yadayadaya... (Don't know what else to say)

(Spike is an adult in this fic.)

Author's Note: This story idea is from DarknessRising. I was interested in it and thought I would do this as one of my first clopfics. I also would thank Ernest Wood for the editing! Enjoy.

Published 2015-08-12 02:10:02 UTC
Last updated 2015-08-12 02:10:02 UTC

Chapter 1

Spike was free for the night. He decided since he hasn't been with Rarity for some time that he should spend the night with her.

Rarity told him one time that he could meet her any night he was free, but hasn't been free from his duties in such a long time. Organizing the library and making sure the books remained dust free made him so tired sometimes that after he was done for the day, he would sleep all through the night like he was a baby dragon again. But this time, he made the effort of spending this night with the love of his life.

"Hey Twilight, just letting you that I'm going to Rarity's place for a bit. I'll be back before morning," Spike said, leaning in on her door.

"Okay Spike, just be careful not to spend the whole night."

Spike shook his head, sighing and said, "Yes, Twilight." He walked down the stairs and out of the library for Rarity's Boutique Shop.

Walking down the quiet streets of Ponyville, Spike looked up at Luna's moon in all its majesty and said, "Wow... the sky is looking beautiful tonight." Taking his eyes off of the moon he saw Rarity's Boutique in the distance and continued towards it.

As Spike neared the shop, he saw Rarity rather subtly come out of her home draped in a black transparent dress with a black veil over her face. Without a thought, Spike dashed behind a nearby wooden box. He didn't want her to notice him. He then checked to make sure his purple jeans didn't catch any dirt. Spike didn't care much for jeans except for the fact that he had to pay for it, and he wasn't going to let it get dirty or have scratch marks after purchasing it only two days ago.

"What is she doing?" Spike said, looking over the box to see where she was going. He watched at her looking around for a moment and after a few seconds, heading off into the Everfree Forest.

"Why would she go into the Everfree at this time of night?"

He rose up from behind the box and followed her into the forest. Rarity was getting further and further away from his sight, and he was still struggling to get through some bushes and over thick logs that were broken in.

He kept on traveling through the forest until reached the bridge the lead the way to the Castle of the Royal Sisters. Spike then caught a glimpse of Rarity entering into the castle. He had a bad feeling about all of this, but he would do anything to keep her from danger so he went across the bridge as fast as he could.

This isn't like you, he thought, running across the old bridge, being careful not to slip through any cracks in the boards. I know she wouldn't do this, unless something was wrong. I must find out what it is.

Spike made it over the bridge and to the doors of the ruined castle.

"Wow she close these doors fairly quick," Spike said, looking for a small space to open the doors. "Luckily, not all the way." He was able to get his claws in a small groove between the double doors. With a few moments of tugging and pulling, he opened the door up a little and slipped right inside.

The castle was mostly dark for the most part only having lit candles to guide someone through. However, the candles were only lit for a single path. Spike followed the path which had guided him up through the ruined castle leading him to a balcony.

He slowly took a few step forwards, watching at Rarity stare at the full moon. He began to blush as he looked down at her rump through her transparent gown. Spike began to approach her, making another step, but he accidentally kicked a pebble that traveled across and rolled off the edge of the balcony. Rarity's ears went up, and she turned around to see Spike standing at the entrance.

"Spike?" Rarity said removing the veil from her face."W-Whatever are you doing here?"

"That was what I was going to ask you, Rarity" Spike said, looking down at the ground and avoiding contact with her voluptuous body. Despite the kinky feelings he had for, he wanted to help her fight through whatever was bothering her and hold her within his arms and tell that everything was going to be okay.

There was a silent pause between them both. Spike looked at her face filled with trouble. "Rarity... I came to know what was going on with you coming all the way out here at almost midnight? I could see the trouble in your eyes." Spike looked down again, and Rarity had turned around and looked at the full moon.

A small wind passed by, blowing through her mane. The sounds of the forest began filling the ears of them both.

"Ever since that night, you had helped me through such a dark moment, me being that wretched nightmare of the night. That darkness had never left my heart Spike.

"One day of every month, she would break away from my control, and I would change back into the Nightmare," Rarity said, looking down at her chest.

"So then... why didn't you come to Twilight or me? We could have helped you, and we still can," Spike said walking up behind and wrapping his arms around her waist. "You know I would be there no matter what, Rarity."

"Because,"-A pulse was felt from Rarity's body-"Because, I was trying to keep away her lust from.. everyone." She felt her uncontrollable transformation starting to take place. She held her head in pain.

"AAAAAAAAAAAAAAAH!" Rarity screamed.

Spike, hearing the scream, knew something has gone. Wooh, this can't be good, he thought, backing away and watched as she changed back into her nightmare form. Her mane grew longer and began changing into a darker shade of purple, parts of her coat began changing from white to black, and her eyes were changing into reptilian eyes. Her transparent gown and the dark bikini she had below was torn asunder by the sudden expansion of her rump and chest.

The power of her transformation created a force that had knocked Spike off his feet and onto to the ground. The dust of the ruined castle was moving about the area giving Spike a difficult time to see what was going on. But as the winds had calmed and the smoke had disappeared, his eyes laid witness to the most beautiful forms he has ever seen.

"G-Goodness," Spike said as he remained in awe, watching at such beauty. He caught a slight nosebleed that caused a few droplets to land onto his purple jeans. "Aw darn it." He looked down to see his jeans tainted with a few droplets of blood stains. There was even a few droplets on his shirt.

He looked back to Nightmare Rarity, who was watching at him with one eye, her back still turned towards him.

"Hmhmhm, looks like someone managed to tag along."

Spike got up and glared at her, but his eyes could help but look down at her breasts. They were so full, and natural, and garnished like a cake with plum thumb-sized nipples. He was about to utter something when he was immediately cut by the continuation of Nightmare Rarity's talking.

"Oh how I longed for such a moment, where I could satiate all of my hungers. I honestly was getting pissed off that she would keep me suffering like this."

Spike was too confused to understand what she meant by that. All he was focusing on was getting his claws all around the beauty before him.

"Uh..." Spike foolishly spoke, mesmerized in the captivity of her attractive body. Nightmare Rarity smirked turning around and walking towards him. With every step, her breasts bouncing, and swayed her hips teasingly, producing all types of pleasurable inner desires within his mind.

She came up close to him and placed a finger on his snout, smiling. "We need to go to a more secluded part of the castle before we do anything kinky, dear." Her horn lit, and her eyes began to glow. Before Spike knew it, he had ended up within a room that were filled with many candles 'round about. In the middle was a bed fastened with edges of gold, and on top was four soft red pillows, fluffy to the touch.

At the center laid the dark and beautiful damsel, looking at him. She waited.

"Come dear, come and give me love."

"No," Spike said holding his claws to his head. "I want Rarity, back. I want you to be gone."

"Well the only way you're get her back is through me, dear. So unless you don't want to see her again,"-Nightmare Rarity snapped her finger, and Spike disappeared and reappeared on the bed.-"I suggest we get started." She reappeared over him with her hands down on his shirt, and with the lighting of her horn she had torn apart his shirt, revealing his bare chest.

"It will be quite sometime before I am satisfied in my lust, Spike. Uhmhmhmhmhm," She said as she moved her left to his chin, leaning in closer to his lips and pressing her soft breast against his chest. Spike heart began to race, his erection running a bit down his leg. Nightmare Rarity, just inches above his face stopped and looked into his eyes as he looked into hers, blushing, and her breath warm against his snout "Spike... If you want Rarity back. I want for you to make love with me, like how you would make love with her. But let's make ourselves comfortable first first, huh."

Spike closed his eyes and placed his hands at her sides. She smiled, and they kissed. They both began to blush as the time of them kissing went on.

Nightmare Rarity released her lips from Spike's, a line of saliva connected from both of their mouths. She licked her lips and part of it got onto her left breast. She chuckles and looks into Spike's eyes.

"Oh Spike, would you be a dear and take care of this small mess for me?" She grins as his hands slowly slides up her hips along her tummy, then cupping her breasts. She smiles, hefting them up, the soft flesh of her dark tits spilling over her arms and between her fingers. Spike's tongue sliding along the side of his mouth, enjoying every moment of what was happening. She pressed them together and bounced them for him before he began licking away the saliva around her nipples.

"Mmm, make sure it's nice and clean before you begin tugging away dear," Nightmare Rarity said, following with sensual moan. She moved her hands over to her right breast and lifted the tip to her lips. She started to lick her nipple until it became nice and wet then afterwards began suckling on it with a low moan. Spike was finished cleaning the saliva off and began tugging away.

Nightmare Rarity released her right breast and moans as it wobbles just above him. Spike stopped soaking it up and released her left breast. She leaned in, pressing her soft breast on to Spike's bare chest, her blue reptilian diamond eyes peering into his eyes.

"So Spike, how do you like it so far?"

"Uhm, really.. nice?" Spike said with his face red, and his eyes looking away to the side, avoiding her lustful glare.

I don't know if I should be doing all of this with Nightmare Rarity. I should only be doing this with Rarity, and her alone. But I won't see her again if I don't-

"Spike."

"Huh?" Spike said, finding himself within the same room but standing a few inches from the bed and seeing Nightmare Rarity positioned on the edge of the bed, her right hand holding the bed's edge, her legs spread out, and the diamond cutie marks on her soft rump cheeks sparkled away. She knew that Spike really liked gems. It was truly his favorite.

Spike, although feeling a little confused, was washed by the amazing beauty of the flashing gems of her voluptuous rump. His mouth fell open as drool began to drop down from the tip of his reptilian tongue. He placed a finger onto one of her tush's and caused a wrippling like affect all across her beautiful bottom. "Wooh," he mumbled, placing both of his hands upon the vastness of her rear landscape but noticed he forgot to unzip his pants. Spike unzipped and then dropped his pants, and his erection came up against the divide of her dark and rump.

"Mmm, what a wonderful present you have there. It feels good. Why haven't you shown this to Rarity? I'm certain she would be pleased although she wouldn't want to see it." Nightmare Rarity reached back and grabbed his erection. "Step back a bit, darling." Spike obeyed and took two steps back, and she brought his erection right up to the entrance of her anus.  She licked her lips and released her hand from his crotch. Spike felt the strange tingling, pleasurable sensation at the tip of his erection, making him sound out a sensual moan.

"Goodness this feels so good," Spike said.

"Now Spike, I want you to rut me good and cum inside me. And I mean good too."

Spike placed his hands onto her hips and entered his throbbing erection deep within her. "Mmmmm, yeeah, mmph," Nightmare Rarity said afterwards biting down on her bottom lip as Spike continued rutting her deeply, going deeper within her. Her mouth began to open and her tongue came out, dripping with saliva. With each rut, Nightmare Rarity became more like a dog, panting away with the pleasured sensation of his erection moving up and down within her, gripping away at the soft red mattress. Her eyes looking up to the ceiling and her tongue going in and out of her mouth.

"Deeper, deeper!" Nightmare Rarity repeated constantly.

Spike smiled and asked, "Um, how am I doing so far?" He kept on going not giving Nightmare Rarity a chance to respond. She tried to turned her head back but was under too much pleasure to turn even half way. Spike felt that he was nearing his climax regardless.

"Well, not bad for uh! Okay, you're doing, Mmm, Great! You're doing great, darling. Mmph!" Spike increased the speed of his rutting, and Nightmare Rarity continued moaning loudly until he had reached his climax and came inside her. She squealed really loud the almost screeching sound traveled a few miles off away from the castle.

They were both panting from the great pleasure they have given each other. Nightmare Rarity was lying down on her bountiful tits as they cushioned her head like a pillow, and Spike was releasing all the pressure built up in his erection. Nightmare Rarity's horn lit up as she let out a sensual moan. Spike had no idea why she lit her horn, but as he felt his first burst of hot white fluids being released inside her he felt her butt expanded.

He looked down to see if what he had felt was true. As his second burst of fluids were released inside her, he watched as her butt expanded even more, her cutie mark expanding along with it. He pulled out of her anus, a s and was surprised to find his erection was still as hard as before he started.

I don't understand. I could've have sworn just a moment ago I was... done. I didn't think I could go more, spike had thought. But...

"What did you do to me, Nightmare Rarity?"

"Oh, ahmhmhm," Nightmare Rarity rose up from her position. She turned to him "Well I'm not fully satisfied yet, Spikey Wikey. Rarity has been taming me here for months. Being done with it here would be the equivalent of giving an equine, who has hungered for days on end, a glass of water. However, you have nearly satiated my thirst in this case. I want one more go, and I will be done here. And you could have your Rarity back."

"Alright," Spike had responded, scratching his claws.

Nightmare Rarity smiled as she passed her hands of ebony under his scaly chin. She got up from off the edge of the bed and walked around to the leftside of the bed. She gestured, bringing up one of her hands and using her finger to have come forward. Spike slowly came forward, obeying her suggestive command. When he neared her, she moved away her hand down towards the bed.

"I want to do some riding. By the way, did you know that Rarity secretly likes to ride things?" Nightmare Rarity said.

"Why are you telling me this?" Spike said, glaring at her. Nightmare Rarity raised an eyebrow at him. She then sported a smirk.

"You know my dear Spike that  the more you know, the more easier it is to get her. Isn't that you want?" Nightmare Rarity asked as her face had changed to a duck-face expression.

"Uhm... urr-"

Nightmare Rarity took him by the arm and came in closer to him, her breasts pressing up against his chest. Her blue reptilian eyes looking up into his eyes. She, although being Rarity's nightmare entity, still was very much attractive. She brought her arm off from around and away from his. Spike who had been mesmerized by her beauty, sat down and leaned back onto the bed.

She then came and sat up, her butt resting on his legs just below his erection. She then smirked as she bent down and began licking along the stomach, then at the tip of his erection. Spike's erection had squirted up a little pre cum onto her face in which Nightmare Rarity had licked away. "Mmm, tasty. Mmmph, mmm," she went on sucking away. Spike was really aroused by the pleasure he was getting from her.

"Wow this feels really good," he said, watching Nightmare Rarity's head bob up and down, her saliva making his erection really moist and wet, and her tongue moving along it made his erection become harder.

"Okay Rari-, I mean Nightmare Rarity, I think that's.. enough. I feel like.. I going to cum."

She quickly pulled away from his now moist erection and held her thumb down on top the tip of his penis. She came near to his face and kissed him on the cheek. Nightmare Rarity then pulled away and looked at him, her eyes narrowed like a cat's eyes. "Relax Spike, don't cum until I tell you to."

"Ngh, alright," Spike said. She then released her thumb from off the tip and brought her hand down to the mid section of his erection. She rubbed it a few times to make sure it was ready for its task. She then rose up to her knees and placed her wet vagina onto the tip of Spike's penis. Nightmare Rarity went down a little on it, and she let out a small moaning sound.

Although slow, Spike was enjoying every moment of pleasure. He placed both his hands at her waistline, clinging to her hips as she went up and down riding upon and mounting down his pelvis area. Nightmare Rarity let out a small moaning sound, and Spike bit down on his lip as she joyfully rode him.

"Mmph, Mmph, Mmph," was all she repeated, riding up and down on his shaft. Spike loved the sensation he was feeling and felt his climax nearing, but he didn't want to go so soon. He rose up and gripped both her arms.

"Nightmare Rarity... I want you to turn around for me," Spike said. She quickly stopped and was surprised by his request. She dismounted him and rested on his upper legs, her fluids streaming down from her wet pink pussy onto Spike's testicles.

"Why, Spike?" she asked placing her hands onto his chest and leaning in towards him.

Spike smiled and said, "I know I should only be doing this for Rarity only.. but I was always fond of holding your tits. I feel as though I have touched the heavens holding and squeezing them."

Nightmare Rarity smiled and licked her lips, turning and then leaning onto him. "Well, you did ask nicely." She placed her hands onto his legs and mounted him, going down on his erection slowing. She felt him go all the way inside her, and the pleasure felt magnificent for her. "Mmmph... ya know, you should just ask her out. I'm sure she would enjoy what you have given to me on this night."

Spike thought about it for a bit. Although his feelings was mixed with pleasure and confusion at that moment, he smiled and said, "I don't think I'm ready yet and not for anytime soon." He leaned his head in on her shoulder and held up both her breasts in his hands, the overflowing surplus of soft dark flesh in between his fingers. "The night is pretty much gone,"-he looked out the entrance of the room, down the hall and at the balcony that seemed to carrying the light of the morning dawn-"and I should have been back at the library for some time now. Let us finish, shall we." He gripped the soft tips of her nipples and squeezed, causing Nightmare Rarity to moan some more.

Nightmare Rarity continued riding him up and down. They both had reached their climax and came. Spike felt all of his fluids go up inside of her and he felt her clamp down on him in her own climax. "Hmph, well done Spike." She leaned back and kissed him afterwards, wrapping her arm around his neck. Spike's erection had begun deflating, and he didn't feel he could go anymore. She slowly dismounted him and turned around, nestling back down and leaning into his embrace. She placed her hands on his firm chest, looking up into his eyes. Spike looked down into her eyes, and his eyes had then widened as he noticed the brightening of her skin.

He watched her pupils changed change from reptilian to normal blue eyes. As her skin became as white as snow, she smiled and said, "Thank you, Spike. I could.. finally be.. at ease again..."

Nightmare Rarity, who was finally Rarity, eyes had closed and her head came down onto his chest. Spike, who became tired afterwards, fighting to keep his eyes open, saw her sleeping down soundly on his chest. It was a moment that always wanted to see, but he didn't have the energy to stay up the rest of the night. Despite its small disappointment, he was happy that from then on he could remember this picture... this very moment. A moment he could cherish for a long while to come.

"I'm going to cherish this picture. Just before my eyes gives up on me, I will keep it focus on your beauty, Rarity. You being this close to my embrace is something.. I've longed for," Spike used the last of his energy to put his hands onto her back, but his eyes had closed before he could get around to completing a task he secretly wanted done for a long time.