Rarity and Sweetie Belle looked across the table in the bedroom and playroom of their house at each other with lust and love as they talked, planning on what they would do that evening. The two had become a couple within a year after Sweetie turned eighteen, and it hadn't taken much time after that for Rarity to become the pinnacle of submissiveness towards her dominant little sister.

"So, as we agreed, you'll be tied up, we'll have a varied level of discipline, followed by a cool-down period and finally sex, correct?" Sweetie Belle asked her lovely sister sub.

Rarity smiled happily "Yes, Mistress. You'll discipline your naughty little slave and then fuck her so good!" Her eyes twinkled in lust at that statement.

Sweetie smirked and shook her head. "I'm not sure what you're looking forward to more, my discipline or getting fucked stupid."

"Must I decide?" Rarity batted her beautiful sapphire eyes at her lover.

Sweetie walked over and smacked her butt playfully. "You little scamp. It's almost like you want to start our session now instead of an hour after dinner."

"Mistress, your cum is delicious, but I think I'd rather eat regular food first, just so I only pass out from pleasure, as opposed to hunger." Rarity opined after letting out a coo at the spank.

Sweetie Belle nodded. "Fair enough. Let's go see if your stuffed portabella mushrooms are done."

Rarity sweetly asked. "May I have some of that fantastic zinfandel with it, Mistress?"

She nodded. "You may have two glasses, no more." She planned to have only one glass herself, but her submissive big sister only became more passionate with a moderate amount of wine.

"Yes Mistress." The privately meek mare replied.

The two sisters went off into the dining room to have their romantic dinner.

Having enjoyed a delicious meal and an hour to let their food digest, the two incestuous siblings returned to their playroom for their planned evening of fun. Sweetie Belle delicately placed a special ring over Rarity's horn. Not an inhibitor ring as might be placed on a criminal, but a draw ring, an item that would redirect all magic, active, passive and orgasmic into specifically linked items and enchantments.

Sweetie Belle giggled. "The perfect wedding ring for you, my lovely slut."

Rarity shivered as she felt her magic being redirected away from her control. "With that ring, I do thee wed, Mistress." Finishing their ritual joke.

Sweetie Belle smiled, then brought up the ring and plug gag combo and eased it into her sister's mouth. "Comfortable fit?"

Rarity flexed her mouth a little around the oral obstruction, then nodded with a single grunt.

Sweetie Belle then proceeded to cinch the gag harness in place, leaving a little give for comfort. Following that, Sweetie channeled some lime green magic into a section of magical silk rope on the floor, mixing with a bit of her sister's borrowed magic.

The rope slowly began to rise up into the air, and then began to crisscross each other over Rarity's body, binding her in such a way that she couldn't move while in suspension, yet comfortably supported.

Once again, Sweetie Belle began checking the ropes for places where it was too tight or too loose and would endanger her precious submissive sister. Satisfied with her check, she asked Rarity "Comfy? Ropes feeling good?"

Rarity responded with an enthusiastic nod and sensuous moan.

Sweetie Belle grinned viciously. "Excellent." With an arcane twist of her fingers, Sweetie Belle grabbed her sister's wondrous breasts and began to massage, causing an immediate effect. Rarity's breasts slowly began to expand outward from pert and perky tits to much larger mammaries that might even be described as udders with a drawn out pleasured moan. "Mmm, you're such a good subject for expansion magic, Rarity. Well, really all sex magic. I suppose it's part of why you became mine in the first place."

Stepping back towards a table with various tools and implements, Sweetie Belle grabbed two small items before returning to her sister. Moving her hands in more blatant yet potent mystic passes, Sweetie Belle channeled magic into the spell form before grabbing her sister's newly bountiful chest, a gurgling noise arising from the now filling udders. "Now to see if your milk is as sweet as always, dear cow." She taunted before suckling at her sister's left nipple.

Sweetie Belle sucked from that nipple for a good three minutes, swallowing her sister's delicious dairy cream before pulling back. "Ah, delectable as always."

Following those words, Rarity soon felt two hard pinches on her nipples that soon combined with a constant sucking sensation. Her nipples had been clamped! Craning her head down, she noticed that there was a blue tinge on the clamps, causing her to look at her sister with a question in her eyes.

"I see you've noticed your magic feeding into the clamps, and are wondering what's going on. Well, I came up with a pair of nipple clamps that would both clamp and suck on a subject's nipples, providing both pain and the pleasure of being constantly suckled and drained. Your milk even goes to an extra-dimensional tank I've set up for it."

Rarity did the only thing she could do at this information, moan as her breasts were simultaneously tortured and pleasured, causing her arousal to drip on the floor.

Sweetie Belle chuckled as she heard the drops hitting the floor. "Needy little slut." She then grabbed a black silk scarf and used it to deny her sister her sight. "Can't have you anticipating what's going to come from where." She taunted.

Rarity hung there, a hogtied horny sub slut of a woman, desperately hoping for some sort of sensation, then 'crack!', right on her right ass cheek, a hard hit with a paddle, sending a paroxysm of pained pleasure through the masochistic mare as she jolted against her bonds. A delicate hand fell upon that same ass cheek, gently rubbing away some of the sting before another crack, this time a hand, right on the side of her left breast, causing her to moan loudly as her milk flow increased at the treatment.

The now reddening spot was in turn massaged, but not long before a dull, almost uncomfortably warm, slim metal object was traced over her right breast and down towards her stomach, teasing her navel for a moment before another hit with the paddle, this time on her left ass cheek, causing Rarity to scream out in pleasured pain as she had her first orgasm of the evening, soaking the floor beneath her.

Sweetie Belle stated in an amused voice. "My my, you really were worked up, weren't you?" A quick smack against her right breast was followed by more words. "I'm going to see if I can't wring another two orgasms from you before we take our break."

Following that statement, Rarity was paddled, teased, spanked, and subjected to objects both hot and cold, seemingly driving her insane as her juices flowed freely from her pussy, three orgasms ripped from her body in rapid succession.

Sweetie Belle noted with some surprise. "I guess I wasn't understating things when I said you were worked up. I guess I'll have to reward you with something unexpected."

Rarity shook within her bonds, curious yet slightly worried about what her sister might do to her as a so-called reward until a slim tongue flowed over her slit, teasing her lips and drawing a grunt of pure pleasure from her mouth. Sweetie Belle repeated the teasing lick before slowly pushing her tongue inside her sister's tight pussy and slowly moving up and down in her quim. Sweetie Belle remembered a certain technique that always drove her slave sister wild, and began to put it into play. Sweetie started by writing a big capital R inside of Rarity's box with her nimble tongue. A capital A followed it, followed by other capital letters spelling out R-I-T-Y, causing Rarity to spasm in a mild orgasm.

Swallowing down some of the fluid, Sweetie Belle continues to write with her tongue. Y-O-U A-R-E M-Y S-L-A-V-E A-N-D Y-O-U S-H-A-L-L B-E M-I-N-E F-O-R-E-V-E-R! And with the exclamation point, Rarity shuddered in a massive orgasm, passing out as she came while soaking Sweetie Belle's face and floor.

A few minutes later, and Rarity slowly awoke to her sight restored and Sweetie Belle's erection near her mouth while strong yet gentle hands massaged her bound and welted body.

"I'm not going to let you out of your bondage quite yet, Rarity, but I do think it's time we stopped for something of a break. I will, however, give you one of your favorite beverages." Sweetie Belle removed the plug assembly from Rarity's mouth, exposing the ring gag and forced open mouth within.

Rarity lunged as best she could while bound and suspended, trying to engulf her Mistress's delicious cock with her mouth, but unfortunately just barely missing it.

Sweetie Belle smiled and smacked Rarity's face with it before pushing it into her mouth. "Silly slut, I can see that you're decidedly hungry for my cock."

Rarity did her best to convey an uh-huh through both phallus and ring-gag, which ended up mostly being a whorish moan that tickled her owner's pillar of flesh before desperately sucking more and more of the futa-meat into her mouth. Rarity got half of her Mistress and sister's dick into her mouth before it finally hit her throat. Suppressing her gag reflex while taking a deep breath, Rarity pushed her face as far forward as she could, deepthroating her sister and causing her eyes to water, her mascara starting to run.

Sweetie Belle stopped massing her sister's body for a moment and commented "That whorish look of your mascara running like that is an excellent look for you, slut."

Rarity deeply blushed, and continued to fuck her throat on her owner's throbbing flesh-pillar at an increased pace, desperately seeking her sister's delicious and plentiful seed. She can't help but moan harder and louder, gasping in musk-scented air around Sweetie Belle's voluminous prick as she can, driving her to greater heights of lust drunkenness. Her nimble tongue pressed against and massaged the delicious cock in almost desperation for her owner's off-white bounty.

Sweetie Belle slowly rocks and forth against Rarity's immense cock lust, tempering her own desire as she cast a spell to increase the density of her own musk along with bringing her virility up to new heights. However, she did consider a point of pride that she could control her orgasm nigh-perfectly, and so decided to merely let her sister tire herself out pleasuring her erection.

Rarity finally began to slow down her pace in inhaling her lover's cock, and looked up at her with frustrated tears in her eyes and whimpers of pure lust coming from her dick-stuffed visage. She finally stopped for a moment, leaving her ring-gagged lips at the base of Sweetie Belle's dong.

Taking pity on her sub, Sweetie decided to go ahead and bring about her own orgasm, and began to fuck Rarity's mouth and throat like she would a cheap whore's pussy for a minute before hilting herself in Rarity's mouth and cumming into her stomach, bypassing her mouth and throat completely. Gush after gush of cum went into Rarity's stomach, thicker than glue and potent enough to impregnate an entire city's worth of mares. Sweetie Belle began to pull back as her orgasm tapered off, watching as Rarity's stomach began to inflate from the massive amount of cum that had been forced into it. Rarity took the last few loads directly in her mouth, doing her best to swallow everything avoid spilling any of her mistress's precious seed from her mouth, but not entirely succeeding.

Sweetie Belle chides her wasteful slave. "Tsk tsk, can't even swallow all of my cum. Though I suppose it's to be expected. There was an awful lot. I suppose I'll just have to help you out." With that, a light green glow gathered up the puddle of spilled cum and rolled it into an off-white ball of goo that was then pushed into Rarity's mouth.

Rarity managed to swallow the cum that had been pressed into her mouth, and smiled around her ring-gag at her mistress to show that she'd swallowed all of it.

Sweetie Belle channeled some magic into the ropes, causing Rarity to be lifted up into a comfortable standing position, yet still suspended from the ceiling and limbs held mostly immobile. She gently removed the ring-gag from her sister's mouth before kissing her deeply and fully. The kiss went on for a long time, Sweetie dominating her sister's mouth with her tongue, almost pushing her tongue down her sister's throat. Finally, Sweetie broke the kiss, pulling away from her slave's sweet lips. "Your mouth tastes so much sweeter with my cum in it, my slut."

"I'm glad you like it, mistress, because your cum is a delicious treat!" Rarity said with a satisfied smile.

A lascivious grin crossed Sweetie Belle's face. "One I'm always happy to give you. But I think I'll give your other lips a treat, how does that sound?"

Rarity looked desperately at her sister. "Please, mistress, fuck me!"

Sweetie Belle placed the plug assembly back into the ring gag, then re-gagged her sister. "By all means, slut. I'll be happy to."

Sweetie Belle wasted no time and began thrusting hard into her sister's pussy, stretching it wonderfully, filling her completely. Rarity moaned into her gag in response. "You're always so tight, slut, even after all this time. Something we can thank your exercise routine and my spells on, I suppose." Rarity nodded in reply, trying to thrust back against the invading pillar of flesh. Sweetie grabbed Rarity's hips, and began to pound exuberantly into her fashionista slave's quim. As she thrust, she began to speak. "Rarity, I've been thinking. About something important. A fantasy of mine, that is." Another quick thrust into Rarity brought forth another moan. "I've been thinking about how beautiful you'd be with a belly that's swelling not with my cum, but with my foals. I've thought about how your breasts would grow, and your hips adjust to your belly getting bigger." Rarity nodded while moaning as Sweetie Belle thrust into her curvy body. "Rarity, I want to get you pregnant! Give you as many foals as I possibly can!" Rarity moaned in pure lust and came on her owner's cock. "Rarity, last chance to tell me no. Else you're going to be my broodmare for years to come!" With a heartfelt moan and exuberant nod, Rarity came a second time.

Sweetie Belle gave her sister a kiss on the cheek, then began to channel magic into a delicate spellform created by her hands, before directly stroking her sister's womb with light-green magic. Having finished her spell, Sweetie thrust into Rarity a few more times, and then finally came into her with the strength of an erupting geyser, filling her womb utterly with cum and spraying gobs of the fluid onto the floor of the playroom. She noticed as she fainted against her sister that Rarity herself had been knocked out by the intensity of her own orgasm.

A now untied Rarity sits in her sister's embrace, cuddling up to the dominant younger mare. "I'm going to be a mommy. I can hardly believe it."

Sweetie Belle gives her a brief kiss. "Best believe it, mommy. You're going to get so big with my foals."

Rarity caught onto that. "You keep on saying foals. Is that a statement about repeated breedings, or about the spell giving me more than one?"

Sweetie nods. "Both, actually. I plan to knock you up as many times as I can, but also the spell I used has a tendency for larger than normal births. The rats I tested it on generally had a thirty percent increase in litter size. Now, I don't know how it will effect you, but we should expect at least twins, if not triplets. Though there was that one outlier where the litter tripled in size." A thoughtful look appeared on the sex magic expert unicorn's face.

"Well, daddy, no matter how many foals you give me, I plan on giving all of them all the love I can." Rarity proclaims assuredly.

"We'll do it together, mommy." Sweetie agrees.

And for a time, the kinky couple cuddled together sweetly before Sweetie spoke up. "Well, it's time for us to go to bed, mommy-slut. We should get ready to sleep. Tomorrow we get to work designing your maternity clothes."

"Yes daddy-Mistress." Rarity meekly replied.

And with that, the two of them quickly went about their evening ablutions before they began their final preparation for sleep. Sweetie Belle gently tied Rarity back up into a comfy hogtie, placed a harness about her own waist, and then pushed Rarity down on her cock before tying her down on her cock. "Good night, Rarity." She stated before leaning back and doing her best to start falling asleep.

Rarity replied a very muffled and distorted missive from her bound and stuffed position "Good night, Mistress" and then slowly fell asleep with her owner's cock deep in her throat, their mixed flavors on her tongue and her musk in her lungs.

And as the two of them peacefully slept in this erotic position, Sweetie Belle's dominant seed began to fuse with her submissive sister's seven ova.

Author's Note

My first clop effort that I've actually completed and shared with other people, and full of a lot of fetishes to boot. I hope you enjoyed, and I greatly appreciate constructive criticism.