Dragons and Deception

by PegPony

Rating: mature
Tags: Porn, Fetish, Spike, Non-consensual, Sex, Ember, Profanity, My Little Pony: Friendship is Magic, Alternate Universe, Human, Rarity (EqG)
Length: 5638

Spike fucks human Rarity, meanwhile Sludge is fucking Ember

Spike is now in a relationship with his life-long crush Rarity after applying Sludge's technique of fucking her into submission and forcing a relationship. Spike then figures, why quit there? Might as well go to the human world and conquer the human Rarity as well! While he is off on that mission, Sludge is called to the dragon lands by Ember for breeding purposes.

This story was written for: osmar lael & I_am_IronPony

Published 2022-01-19 01:10:00 UTC
Last updated 2022-01-19 01:10:00 UTC

Sadistic Spike

As Spike tumbled to the ground, he was relieved to find that he had indeed retained his dragon form upon stepping through the portal, much more comfortable than being a dog that's for sure. Though the one thing he wasn't too happy about was that it appeared that for some strange reason, he had arrived back at Canterlot High during the night, when the school was closed and all of the students were at home and asleep. Then he had an epiphany, this would actually be somewhat ideal, he knew from his last adventure where all the girls lived so all he had to do was journey to Rarity's house and after putting his dad's advice to use, the human version of Rarity would be his, why have one Rarity when you can have two?

As he started making his way to Rarity's home, it also occurred to him that Rarity would most likely be alone, her parents were always travelling around so she practically had the place to herself. Forcing her to comply with his demands would be so much easier without anyone being able to interfere and though he wasn't a malicious individual, he had ways of ensuring she couldn't get help if things went wrong, he was already getting hard at the thought of it. Upon reaching her house he encountered a problem, how would he get in? It was as he was thinking this that he heard Rarity's voice from a nearby window, getting a close look he could see that he'd gotten there in time, she was in some deep blue silky pajamas but she hadn't gone to bed yet! Smiling at his good fortune, he confidently knocked on the door and waited for Rarity to arrive and let him in, in more ways than one.

As Rarity heard a knocking at the door she huffed and went "Goodness me, who could this be at this rather late hour? Has Sweetie Belle come back from her slumber party?" Rarity walked to the door and when she opened it, waiting there was a green and purple dragon, she was shocked until she remembered that a particular talking dog with the same color palette had mentioned that he was, in actuality, a dragon and she smiled as she went "Spike? Is that you? You're a dragon!"

Spike nodded and went "Yes indeed! I am a dragon! Princess Twilight helped me find a little spell so that I could visit, cool huh?"

Rarity chuckled and said "I'll say! I never expected you to return, especially not as a dragon! Why have you decided to visit anyhow?"

Spike went "Well I know that Fluttershy is fascinated by animals and since I'm not exactly part of this world, I figured she might wanna ask me some questions about dragons, though from the looks of it my timing isn't exactly perfect"

Rarity nodded in agreement "Yes, I dare say that Fluttershy will be asleep by now and I doubt there are any suitable lodgings for... wait, if that's the case then why come to my house?"

Rarity was asking a lot of questions that would have made any other dragon panic about having to confess they were there for sex purposes, luckily Spike had a good teacher and was perfectly prepared for just such a situation as he calmly said "Well it's just like you said, I have nowhere to stay! So I was hoping you might be able to take me in? Just for the night of course, I will be leaving tomorrow so you don't have to worry about an extended stay, I wouldn't want to overstay my welcome"

Rarity scoffed and very nonchalantly said "Spike, if you need somewhere to stay, then my home is your home! Come in!" Sweet naive Rarity, she had no idea what she was about to put herself through as she allowed Spike to follow her into her bedroom, the perfect place for him to gain her as a girlfriend through rough sex whether she liked it or not. As they both hopped into bed, Rarity heard Spike making small grunts of discomfort, concerned for the poor dragon she simply asked "Are you alright Spike?"

Spike, with perfect acting, said "Nng... not really, the other reason I said I came at a bad time is because back where I live all the dragons are going into heat..." that was total and utter bullshit, dragons didn't have a heat, though Rarity wouldn't know that... Spike continued and went "I didn't think the effects of it would follow me here but it seems like it has, if I don't find some kind of sexual relief then the chances are that I'm gonna be in excruciating pain for the whole time I'm here, I won't be able to sleep or anything..." another perfect lie.

Rarity had to blush, Spike was basically saying he needed to blow a load or he'd suffer, the poor thing! With genuine sympathy, Rarity went "Oh... oh dear well, that simply won't do will it? Are you able to... um, you know.... "help yourself" as it were?"

Spike shook his head and said "No, doing that won't make it happen, I need someone to do stuff with if I'm ever gonna feel better", Spike was laying down a lie lasagna and Rarity was swallowing down every spoonful, though soon she'd be swallowing something else entirely. Rarity bit her lip, she wanted to help him but, needless to say, the prospect of sexually pleasing a dragon was a little daunting and it wasn't exactly on her to-do list... she weighed up the pros and cons in her head and made the decision right then and there.

"Well Spike..." said Rarity "In the interest of helping you alleviate your... um... let's call it "stress", perhaps I could be of service?" Spike grinned to himself, Rarity had taken the bait, hook, line and sinker, she was practically his already.

Spike, still playing innocent, went "Really? You'd do that for me?"

Rarity simply went "Of course! It would be cruel to leave you in such a state and I do pride myself on my generosity, though if I want to get some sleep it doesn't seem like I have that much of a choice either, though I digress! Just tell me what you want and I'll do it for you"

Spike went "Well, I suppose a blow job wouldn't be a bad start", Spike sat up and removed the covers from his waist, revealing his rather impressive and almost intimidating monster cock.

Rarity's eyes were wide as she slowly maneuvered herself in between Spike's legs, ready to go down on him, though as she stared at the enormity of dragon dick she was tasked with pleasing, she couldn't help but doubt her ability to suck him off. "Holy shit..." said Rarity "You... you're fucking massive!" Rarity's pussy moistened as the thick and heavy masculine smell of his junk graced her nostrils, her mouth watered as she wondered if he would taste just as powerfully arousing as his musky scent suggested. Spike just watched with a smug grin on his face as Rarity took hold of his shaft and dragged her tongue across his full sagging nut sack, making her shudder as the salty tang of his soft and sweaty skin danced along her taste buds. Rarity gently cupped his balls in one hand and rolled them around in her fingers, she moved upwards with her slick salivating tongue leaving a shiny spit trail as she licked his cock from base to tip before closing her eyes and softly moaning upon engulfing the tip of Spike's member into her mouth, suckling on his sensitive prick.

Spike just let out a sigh of contentment and pleasure, moving a claw to rest on Rarity's head as she delicately worked to get her first taste of Spike's pre cum. As the first few beads of his pre landed on her tongue, it tasted pretty much as she expected it to taste, surprisingly delicious. With her own personal goal achieved, Rarity began to descend and slide even more of Spike's length into her mouth to achieve her new personal goal of sucking on his fat tasty schlong until the horny dragon nutted in her mouth. Spike just groaned as he felt Rarity's lips glide along his skin as more and more of his stiff erection was bathed in the wet embrace of her mouth, it wouldn't be long now before he was ready to take charge and fuck her face, once he did that then nothing could stop him and Rarity would belong to him. Rarity got an impressive two thirds of the way down before she could feel the tip of his cock in the back of her throat, Rarity felt slightly smug that she had managed to take so much dick in her mouth before it came too close to triggering her gag reflex, she pulled back until just the head of cock remained in her pursed lips, before swiftly going all the way back down again.

Spike groaned as he felt Rarity bob her head up and down on his throbbing erection, his orgasm was imminent and the feeling only got stronger when Rarity gently squeezed his balls as if to encourage them to unleash their load. A minute or so went by with Rarity keeping up a consistent and constant pleasurable pace as she dutifully blew Spike, getting herself into a relaxed yet erotic rhythm as she enjoyed the simple pleasure of sucking off a dragon, the taste, the smell, the texture... it was all so intoxicating. Spike wasn't going to last much longer, so he decided that now was the time to assert his dominance, Rarity's calm and sensual approach was interrupted when, much to her shock, Spike grabbed onto her head and forced every last inch of his reptilian rod into Rarity's mouth before feverishly fucking her face. Rarity immediately started to hack and cough around the enormity of thick fuck flesh that was currently violating her throat, she wasn't exactly prepared to be so roughly taken, let alone deep-throat such a tantalizingly yummy fuck stick, the deep oral penetration only continued as Spike's balls kept slapping against her chin, her nose being pushed up against his groin over and over again.

Spike moaned in ecstasy as he pushed Rarity down one last time before saying "Oooh fuck yeah! Swallow it all bitch! Every last fucking drop!" Rarity was forced to put up with and endure a few seconds without breathing as Spike fired off several ropes of spunk down her throat and directly into her stomach, once he had finished he relaxed with a contented sigh, while Rarity immediately pulled herself off of his member, coughing violently with a red face, gasping for air as rivulets of saliva hung between her lips and Spike's cum cannon, drool dripping down her chin.

As Rarity tried to tame her frazzled hair and blink back the tears of exhaustion in her eyes, she cleared her throat and, slightly hoarsely, said "Spike... I'm glad you enjoyed my ministrations, however it is rather rude to make your partner swallow your payload without even asking!"

Spike smirked and said "Sorry, I guess I got a little carried away, didn't mean to treat you like a whore", Rarity blushed, although she had said Spike was rude for just having his way with her, she had to admit to herself that she didn't necessarily find it unenjoyable. Rarity assumed they were finished until she saw that Spike's boner hadn't gone down, even after ejaculating he was still just as hard as before the blow job even began. Spike followed her line of sight then chuckled as he said "Oh, I guess I forgot to mention that once isn't really enough for a dragon huh? Sorry Rarity but you're gonna have to make me nut a couple of times before I'm totally drained, how about you let me cram my dick into your sweet, tight little pussy?"

Rarity's eyes widened, her pussy was wet and aching but she wasn't sure that was she was ready to let Spike fuck her, she hesitated as she went "You... it's just... just this one time? Right?"

Spike just grinned and went "Yeah! Sure!" Rarity was blissfully unaware that soon Spike would own her and that her pussy would get plenty of action whenever he decided to visit the human world. Rarity began removing her pajama bottoms, trying to ignore the embarrassingly large dark and damp patch that had formed in the crotch during the blow job, and threw them aside before quickly lying on her back and opening her legs to reveal her moist pink pussy. Spike practically salivated as he watched Rarity use her fingers to open up her quivering pussy lips, parting her fleshy folds like she was inviting the nearest cock to slam itself in and make itself at home in her cunt.

As Spike made his way over he held Rarity's thighs apart and starting aiming the head of his dick towards her waiting entrance, Rarity sighed to herself and said "I can't believe I'm about to let a dragon fuck me...", not even a second later, Rarity squealed upon Spike launching his hips forward and burying himself balls deep inside Rarity, stretching the walls of her hot and squeezing fuck hole.

Spike chuckled as he began pumping away at Rarity's pussy, it felt looser than he imagined it being, it was tight for sure but not quite as tight as the other Rarity, who was still quite tight even after Sludge had wrecked her perfect pussy. Spike said "You're taking this quite easily, who else has been inside you?"

Rarity held back shrieks of ecstasy as she said "Aah.. I... I let a guy fuck me yesterday because... ooohhhh because none of the girls at school wanted him!" Spike had to hold back a laugh, Rarity was too generous for her own good, she wasn't the kind of girl to be a total slut but if she had to have sex for the sake of being generous then she'd do it. Spike pounded harder, it seemed both versions of Rarity were a case of sloppy seconds, not that Spike was complaining, soon enough the human Rarity would only crave him and him alone, her body would mold to him just like pony Rarity did. Spike leaned forward and grabbed onto Rarity's shoulders, pinning her down as he drove himself as deep as he could, the tip of his cock pressing against her cervix. the second that Rarity felt her cervix being pressed on, she almost screamed as she instinctively wrapped her legs around Spike's waist and convulsed in orgasm, her juices soaked Spike's cock as her pussy clenched mercilessly, squirting her female fuck fluids out around the mass of dragon dong still entombed in her baby maker. Spike began losing control, being bathed in the warmth of her wet flesh was proving to be too much for the young dragon as he began thrusting like he had gone mad, pistoning his hips and fucking Rarity in a way that made the both of them feel twinges of pain and discomfort.

Spike gritted his teeth as he hilted himself and groaned intensely as he blew a fat heavy load in Rarity's depths, neither of them knew if he could impregnate her or not, but they didn't care. Rarity was a mess by the time Spike had filled her cunny with dick cream, sweaty and shuddering in the aftershocks of orgasm, Rarity caught her breath and said "My... my goodness, I think it's time for bed, after all we both need our slee-aah!" Rarity failed to finish what she was trying to say when Spike yanked his tool out of her gaping pussy and, with no warning and seemingly no effort, re-positioned himself and slammed his cock all the way up Rarity's ass.

You can't spell "member" without Ember.

Spike held Rarity in his arms and fell backwards, ensuring that he ended up on his back with Rarity on top of him in the cowgirl position. Spike gripped Rarity's hips and barked at her "Ride! Ignore the excruciating pain you must be feeling from having your anal virginity taken and ride me! My cock is already in your tight booty so you might as well get going and try to enjoy yourself!" Spike punctuated the end of his sentence with a swat to Rarity's left ass cheek, after seeing that Spike wouldn't be taking no for an answer, she did the only thing she could and started bouncing herself up and down on Spike's lap and focused on relaxing so she could enjoy having her butt filled with huge veiny cock. Rarity was beginning to pant, the exertion and energy of all of this sex was making her overheat, she rode even harder and faster as she basically tore off her pajama top, allowing her decently sized tits to jiggle with every movement she made. Spike grinned and said "Yeah, for a girl who spends most of her time making clothes it's incredible that you've never realized how fucking good you look when you're naked, especially when you're working to make me nut in your butt... damn your ass feels good, I'm glad to see you've taken a liking to having your rump filled so quickly and easily, you'll earn the right to have my fat sticky load deposited up there in no time..."

It was true, the more Rarity accepted her fate, the more pleasure she felt, the more actively she started wanting Spike to claim her rear, even if he was only doing it to conquer her body. Rarity increased her rhythm, the incredible feeling of fullness in her bottom driving her to get Spike closer and closer to his climax as a sign of gratitude, Spike welcomed it happily, it wasn't as wet as her pussy or her mouth but damn was her ass so hot and so so damn tight, hugging his cock like a soft fleshy glove jerking him off. Once Rarity had fully embraced the butt fucking she was willingly engaging in, she groaned when her pussy clamped down on nothing as she experienced yet another maddeningly strong orgasm, soaking Spike's midriff with her gushing fuck hole. The caress of Rarity's anal walls became too much, seconds later Spike joined in with Rarity as he grunted huskily, his nuts once again tensed and his cock pulsed while he spilled a full virile load deep inside Rarity's behind. When they both came down from their high and were about to enter a satisfying afterglow, Spike was the one who got a surprise when when Rarity lifted herself up off of his cock, only to lie down, take his dick into her cleavage and start rubbing her tits up and down his slick length.

As Spike looked down to where Rarity was massaging his still sensitive prick, he saw Rarity staring back with a frightening smile and wild bloodshot eyes. Rarity kept up her boob job and said "Yeah? You like these tits you filthy little shit?! You're still fucking hard, so nut for me you bitch! Do it all over my face and chest! I don't care if you're a dragon or a dog when you visit, so long as you're constantly raping me then I'm happy! I don't give a shit so just cum for me! Cum cum cum cum cum cum cum FUCKING CUM!!!" Spike was hardly able to turn down that request and so, the final load he had to give was sent rocketing out from his cock, strands of it landing all over Rarity's face and onto her breasts. When he finished, Rarity rolled over, giggling like an insane woman with tears streaming down her face until she fell asleep. Spike got up after a quick rest and returned to Equestria with a job well done, now he had two versions of Rarity who would beg and plead that he hurt and dominate them as much possible.

meanwhile -

As soon as Spike had left for the human world, Sludge had to fly to the dragon lands due to being summoned by none other than dragon lord Ember. Sludge wasn't sure why he had been summoned and if he was being honest with himself he would've preferred to stay in Ponyville so he could keep banging Twilight, who had become borderline obsessed with having Sludge pound her holes at every opportunity no matter how bruised she got after a fuck session when he was feeling more horny than usual. As Sludge clumsily landed in the dragon lands, he looked up to see Ember looking at him with a somewhat neutral look on her face, almost as if she wasn't happy to see him but wasn't unhappy either. Sludge dusted himself down and said "You wished to see me?"

Ember nodded and said "Sludge, you are Spike's father, is this correct?"

Sludge panicked briefly, only to realize that he could easily keep up the lie, how could she check? Nobody knew who found Spike and where, there was no way Ember would be able to figure out if he was lying, might as well keep up the charade! Sludge cleared his throat and confidently said "Yes! I am Spike's father!"

Ember continued by going "Spike's mother is deceased, is this also correct?"

Sludge nodded, making sure he seemed somber and sighed out a "Yes... his mother is... no longer with us"

Ember hummed in thought "Very well Sludge. I wish to give Spike a mother here in the dragon lands and at the same time I also wish for there to be more dragons like him, I don't know what it is about your genetics or lineage but Spike is different to other dragons, strong, compassionate, he embodies everything I want for the future of our race. So, if you are willing, my third wish is for you to breed me"

There was a moment of silence, Sludge was surprised to say the least, he had just been given the opportunity to mate with Ember, the most powerful and arguably most attractive dragon in the dragon lands. Sludge figured if he was to take Ember up on her most generous offer, he may as well see what else he could get out of it while he still could and make sure he wasn't stuck with only Ember as a sexual partner, Sludge simply went "I have some questions"

Ember nodded and said "Go ahead"

Sludge said "So... in terms of us having sex, is your pussy the only thing I get to stick my dick in?"

Ember went "It may come as a surprise that while I will try to avoid unnecessary touching of your cock, I am willing to be somewhat accommodating. I can use my mouth to make you erect and I'll even let you take my rump, that is as far as I'm willing to go and is not something I ever intend to negotiate"

Sludge was happy with that, though considered it a shame that she was only willing to blow him to get him hard, Sludge's next question was "OK, well are you the only sexual partner I get to have?"

Ember rolled her eyes and went "No, fuck whoever you want, stick your dick in a beehive for all I care. So long as you're willing to fuck me every now and then for breeding purposes, or for pleasure if you like, then you can do whoever you want"

Sludge had one last query, this was the one he was most scared of as he said "How much involvement do you want from me... like, in terms of being a parent?"

Ember simply went "However much involvement you want, I want you for your DNA, not your skill as a father, so you can be a dad to all the children you give me or you can completely ignore them, either way is fine", well, that put all of Sludge's worries to rest, time to get the show on the road!

Sludge said "OK Ember, let's do this!" Sludge's cock was already hardening at the prospect of being able to claim her, which in and of itself was quite a feat. Dragon lords had a history of being very picky when it came to sex, it was lucky that Ember was so woke, or at least as woke as a dragon lord could get when it came to prudishness in sex. Ember silently just dropped to her knees in front of Sludge and effortlessly slid his entire cock into her mouth in one go, almost sucking him off in a violent way as she coiled her tongue around his shaft. Sludge wasn't expecting such a quick impromptu blow job and gasped "Holy shit! Whew... damn.." as he placed a claw on Ember's head, which she quickly slapped away as she began moving back and forth. Ember was giving a really good blow job... for about two minutes, the second Sludge was fully erect she pulled herself off of his cock, which would have been disappointing had she not immediately got on her back with her legs wide open to invite Sludge to penetrate a much more pleasurable hole. Sludge, in true dragon fashion, practically threw himself onto Ember and rammed himself into her pussy, immediately thrusting as fast as his fat lethargic lizard body would allow.

Ember grunted and said "Sludge... nng... while I... aahh... appreciate your desire to... oohh... to breed me as efficiently... grr... as possible, I think it... fuck... it would be better if you... holy shit... slowed down a bit!" Unfortunately that request fell on deaf ears, if anything Sludge only became more eager to fuck her as hard as possible, though it wasn't like he could help it. Sludge never ever got any action in the dragon lands and while ponies where more relaxed and soft when it came to sex, nothing could compare to a dragon, at least not to a dragon. It soon became clear that Sludge wasn't exactly a great lover when it came to making sure the one who had been gracious enough to receive him got to enjoy it as well, he could last a decent amount of time with a pony because while the sex was nice, it was less nice than the inside of a dragon female, the problem being that now he was fucking a dragon female he came after only a minute or so of humping away at her pussy. While Ember did consider it pathetic that Sludge couldn't last very long, she wasn't really complaining, the way he had sex was clumsy and she didn't even really find him all that attractive either, she was simply thinking of the exceptional children she would get to bear.

Sludge pulled out, gasping for breath as he said "Sorry Ember... I've-"

Ember raised her claw and said "Don't apologize, believe me when I say your fast and furious pace was beneficial for the both of us", Sludge didn't know whether to feel proud or offended, so he just remained silent. Ember spoke once more as she said "Now if I recall the terms of our deal, you want my backside, don't you?" Ember stood up before turning away from Sludge and bending over, calmly sticking out her fat round bottom and waiting for Sludge do what he so obviously wanted to do, fuck it. This time Sludge didn't wanna just hammer away at her, so he decided that rather than going for speed he'd go for strength, why fuck an ass when you had the power to pound it hard enough that you made it hurt in a good way? Sludge clapped his claws onto Ember's ass cheeks as the head of his cock prodded at her pucker, Ember curled her tail around Sludge's torso to keep it out of the way while also encouraging him to move forward and take her rear. Sludge took a deep breath and rammed his cock to the hilt in Ember's back door, his hips slapping up against her thick booty as it jiggled from the force of the impact like two big bowls of jello.

Ember groaned at the rough penetration and slight discomfort of being so suddenly filled, she looked back over shoulder at Sludge and said "Geez, wanna hold yourself back there big guy? I know I've got a sexy ass but that doesn't mean you have to slam your big stupid cock up there like a fucking battering ram", Sludge had no response to give as he continued his motion of long, hard thrusts, pulling out until just the head of cock was still in then sliding all the way back as hard and as deeply as possible, paying no heed to Ember's slight annoyance at how he had chosen to go with repeated powerful thrusts with a three to five second interval in between each one. However, this did benefit the both of them, Sludge was enjoying the confines of her caboose without cumming too soon and, despite her growls and grunts, Ember was actually really enjoying herself, having already experienced a very well-hidden orgasm three minutes into the anal sex.

Soon enough though, Sludge could feel an all too familiar feeling in his groin and decided to, quite literally, go out with a bang. He spanked Ember's right ass cheek shortly before ramming her fuckable butt at much the same pace that he had used on her pussy, Ember groaned loudly as she experienced another orgasm, slightly weaker than the last one, shortly before Sludge made the same noise and filled her rear entrance with thick ropes of hot, heavy spunk. Ember unfurled her tail and allowed Sludge to pull his cock out of her ass, his fuck technique may have needed work but they both knew he had the enthusiasm to make up for it.

months later -

Sludge was having a rather uneventful day in Ponyville, the only really exciting thing that had happened recently was when Spike returned home and proudly declared that he had managed to sexually break and conquer the human version of Rarity, something which made Sludge extremely proud. Sludge walked into the castle and was faced with a rather interesting sight, Twilight, Rarity and Ember were all stood there with ridiculously large bellies as a result of being heavily pregnant, which was a sexy sight, though Sludge didn't fully understand the context. Rarity looked at him and said "So... dragons and ponies are not compatible are they? What the fuck do you call this?"

Sludge shrugged and said "It's not necessarily mine, Spike could be the dad"

Rarity deadpanned and said "I think you're rather missing the point"

Sludge ignored her and said "Well Ember, I know you're happy with your pregnancy, what about you princess?"

Twilight blushed and avoided eye contact as she said "It will be... interesting for study purposes..."

Rarity sighed and said "Well, I can't exactly stay mad, after all Spike and I are so happy together and that is all thanks to you Sludge, despite the unorthodox method of how we both entered into a relationship"

Sludge went "OK, though that doesn't explain what you're all doing here"

They all smirked and gave each other knowing looks before Ember said "Well, all three of us agree that you deserve some kind of reward and since you never got much action in the dragon lands... how about you make up for lost time with us three?"

Sludge grinned as his tool began to throb, today had just gotten a whole lot better.

The End

Author's Note

Thank you osmar lael & I_am_IronPony for this story idea! I hope you enjoyed it :)

Prologue

"OK Spike, I think I've found a spell that should work if I cast it correctly, though I still wish you'd tell me why you intend to go back to the human world as a dragon, from what I understand I'm not sure too many humans would be excited at the prospect of a ferocious fire-breathing dragon running around on the loose in their town", Twilight was stood by the mirror portal with Spike who had insisted that he be allowed to visit the human world in his dragon form, after forcing Rarity into a relationship with the help of some tutoring from his father, Sludge, Spike remembered that there did exist an alternate version of Rarity that he liked but wasn't his yet, so he figured he might as well conquer both versions of Rarity using his father's techniques so that no matter where he went, Rarity would be his and his alone.

Spike said "Relax Twilight! Do I seem like the kind of dragon who could go on a terrifying rampage? Just because my dad has helped me out with my more "dragon-like" side doesn't mean I'm gonna start hoarding gems and finding volcanoes to hang out in, I'll be fine! Besides, all I'm gonna do is visit our other friends, they already know I'm a dragon and I figured I might as well show them, plus Fluttershy would probably love to bombard me with questions about dragon stuff"

Twilight couldn't fault his logic and went "OK, if you're sure", Twilight lit up her horn and focused her magic around Spike. After some bright lights and a strange tingling sensation, the spell ended and Twilight said "Alright, that should do it, have fun!"

Spike smirked to himself and said "Oh, I will" shortly before jumping into the portal.