The five librarians
Twilight Sparkle was alone in her library, filing away books. She'd already filed these books away once, but she wanted to make sure she'd filed them away as best she could, so she was doing it again. It wasn't gripping her like it usually did, though. There was a little, niggling feeling from deep within her loins trying desperately to come out.
There was a reason that Spike had been sent to stay with Rarity for a few days, and that was because Twilight Sparkle, Element of Harmony, student of magic, and practically the adopted daughter of the princess herself, was going into heat. She hated it, hated it with every fibre of her being. Anything that could cause her to lose interest in books was a horrible thing. Back in Canterlot, dealing with it was easy, it was just a spell away, but somepony else had always cast the spell and Twilight had never bothered to learn it. And now she couldn't, because she looked at the book and all of the letters just reminded her of sex positions. Even F. No, especially F.
Twilight sighed, she knew what she had to do. She had to go outside and start degrading herself in front of anypony that would look, in the hope that one of them would rut her silly and give her back the ability to think straight. She hated it.
If only she'd had more time to prepare, she might have been able to think things through. Wait a minute - time! Time was the answer! Twilight couldn't solve her problems now, but she could later! She could travel back in time and cast the spell on herself, letting herself travel back in time to cast the spell on herself, and then she'd be free!
Almost as if it was planned, the moment she'd finished her thought, the room began to shake and the air grew thinner, and the hairs on Twilight's head began to pull apart as the room filled with static. The books around her shuddered and fell to the ground as the very space in front of her began to tear, pure magic forcing its way into the air as a pony's naked form began to emerge, hovering there for her to see. The smooth curves, and long mane, of the silhouetted pony started to drive her wild, the thought of feeling that pony against her body driving everything else from her mind.
Then the magic vanished, leaving a Twilight standing in the center of her library. "Oh, dear! Such a mess, my mistake. One moment, me, I'll clean up!" future-Twilight laughed, picking up the contents of the library with a wave of her horn and filing everything away. Such a display of power and control, Twilight thought - Twilight was gorgeous. She didn't know why she hadn't seen it before. That purple coat looked great on her, and the way she let her mane fall over her body? Glorious.
Twilight knew what she had to do. Running forward, she tackled Twilight to the ground, the raw emotion and energy in her body transforming her into something more beast than mare. Then Twilight kissed Twilight, Twilight shoving her tongue into Twilight's mouth, and tasting herself on her tongue.
"Twilight, what are you doing!" gasped Twilight as she held the ravenous, animalistic version of herself at bay with a field of magic. "I'm meant to cast the spell, and then I go back to my time!"
Twilight gathered her senses enough to start asking questions. "Did it go like that for you?"
"Well, no, I kissed me, but then she pulled me away with her magic, but she started talking about what happened to her and it distracted her enough that I was able to sneak up on her and start licking her ooooh-!" future Twilight responded, blissfully unaware of the cyclic nature of time.
Twilight didn't care, she knew now her plan would work, as she ran her tongue over her other self's body, tasting her own flavour and smelling her own scent. It'd never smelled quite this good.
"Twilight, no! This isn't the plan" future Twilight protested verbally, not lifting a hoof to stop Twilight as her licks travelled downwards, teasingly descending and tantalisingly tasting her coat. "And this isn't going to work! I'm fine, and I've only just had this from future me! Look, turn around already"
Twilight obeyed, putting her faith in the one pony she trusts above all else. She turned around, dropping her front end to the ground as she raised her rear as high as it'd go, her tail automatically raising away and giving Twilight full access to Twilight's puffy, parted slit. "Okay, step 1", future Twilight whispered under her breath as she raised a hoof to her other's backside, tracing a slow line along her cutie mark and marvelling at how little contact it took to make her moan in anticipation.
Step 2 began soon after, as Twilight lowered her head to Twilight's backside, running the end of her nose down until it met the top of Twilight's exposed femininity, taking in the sights and smells of something she never normally got to see. "I wonder how I taste?" she giggled, before giving a testing lick out to the glistening folds and lapping up a little of Twilight's copious juices. "Mmm", she moaned slightly, enjoying her own flavour - it tasted much better fresh than it did from the side of her hoof, she had to admit.
"Do you mind if I-" she began, before being interrupted.
"JUST FIX ME ALREADY" her present-timeline doppelgänger shouted, shifting her head slightly so that her mouth wasn't facing directly into the ground.
Future Twilight didn't need any more encouragement, thinking back to how Future-Future Twilight had done it and trying her best to emulate that - she knew it'd felt fantastic, and wanted to give herself the best treatment she could. Throwing out an enthusiastic tongue, Twilight quickly penetrated herself, feeling her tight walls surround her on both sides, and feeling her own heartbeat pulse against her as the burning heat inside her instinct-driven duplicate rose with the feeling of oncoming relief.
Running her tongue up and down inside of her, Twilight closed her eyes and concentrated on the taste, trying to remember it - she knew exactly what memories she'd be thinking of tonight, when she was unfortunately alone. She concentrated on the sounds, the way each stroke of her tongue exposed another low groan from her enraptured partner, and the way she could hear her forehooves slam against the floor as she struggled to maintain control while her sensitive body was racked with pleasure.
Twilight's heat-stricken body couldn't take it any longer, and her hindlegs gave out, letting her drop a few inches before Future-Twilight caught her in a magic glow, and held her suspended in mid air while she had her way with her. Each lap of her probing tongue brought new sounds from the eager mare, made even louder by the way her mouth was no longer muffled against the floor. Future Twilight couldn't be having that, she was the one who'd have to deal with people hearing - she took a tiny fraction of her mind and put it to work maintaining an anti-sound field around the two, locking the two away from prying ears.
Twilight's groans echoed around the transparent sphere, growing in volume and appearing to increase in number as the sounds bounced back and forth. Future Twilight remembered that, soon after she'd started to hear her own moaning when this was happening to her, Future-Future Twilight had changed tactics.
Sadly removing her tongue, Twilight shifted Twilight around in the air, putting her at an angle and holding her up in mid air. She thought back to the imported magazines she'd once read, about a giant monster that, for some reason, liked to have its way with ponies. She'd never quite understood how such a creature could evolve, but she'd always liked the idea. Now she was going to try and emulate it.
Tapping into the magic deep within her, Twilight conjured up several magical tentacles. Little more than applied telekinesis really, but with a bit of an illusion added in for the shape and form. She was quite proud of her tentacles. Twilight thought back to her own fantasies, and remembered how they were meant to start.
Present-timeline Twilight found herself dropped to the floor, her time-travelling saviour vanishing in a puff of light. In her place lay a gelatinous blob, twice her height, and with dozens of tentacles rippling out of its ill-defined form. No sooner had she seen it, than it had seen her, and it moved - quickly. Faster than Twilight could react, she felt its tentacles wrapping around her limbs, constricting and pulling tight, before it lifted her up and pulled, spreading her legs in every direction. She struggled, but it was no good, the tentacles were too tight and she couldn't move an inch.
More appeared, trailing out from the creature and moving towards her, teasingly exploring her body. They left a wet, slick residue behind, as if they secreted a natural lubricant, and Twilight felt her already burning nethers flare with lust. She needed this thing inside of her. The one small part of her mind responsible for fetishes and fantasies refused to keep silent, though, and shouted her body down. She had to resist. She couldn't let it do what it wants with her without a fight. That was no fun.
A tentacle pressed against Twilight's mouth, and she gritted her jaw, pressing her lips together. Its attempts to penetrate proved fruitless against her clamped jaw, and she felt a small degree of satisfaction. Little had she known, though, that another tentacle had been snaking up behind her, reaching around to her head and wrapping around her horn. It pulled back, quickly and sharply, filling Twilight's head with unimaginable pain as her horn was violently jerked backwards, coming within an instant of fracture, or breakage. The moment her head jerked backwards, and her mouth was open, the tentacle made its move, shooting forward down her throat as she coughed and choked around its girth.
The tentacle started to thrust, forcing its way down her mouth and into her throat, each thrust driving it a little lower. Twilight's throat burned as the lubrication mixed with her saliva and began to trickle down into her stomach, and the tears of her pain hitched a ride on the thrusting tentacle to flow into her mouth.
As if the current punishment wasn't enough, another tentacle shot forward, parting her vaginal lips without a care for her health or pleasure. Twilight felt the skin tear slightly as she had to accommodate its size, its lubrication making each subsequent thrust easy and relatively painless, and each thrust rubbing against her sensitive clit. Twilight moaned around the tentacle currently fucking her throat, and her eyes rolled up in pleasure as she felt a third, thankfully smaller, tentacle probe around her anus, before slowly snaking inside and beginning to rhythmically pump in and out alongside its brothers. Under such punishment, Twilight's lust-driven body couldn't last long, and her body quickly began to jerk and spasm as she underwent an orgasm, the thrusting tentacles driving her over the edge as the stimulated every part of her body, from the three main ones filling her with pleasure and pain, to the dozens of others running their slimy limbs over her form, or to the two that were holding her horn and tail tightly in place so that she couldn't move a single muscle, save for her eyes.
She tried to break free with magic, her brain screaming at her to escape, but the beast easily absorbed the energy she could pull together. She was stuck here. Her tired body was screaming as the tentacles continued, uncaring that she'd already cum, all that did was make their thrusts even easier. Twilight felt her body begin to black out again, the tingling returning to the tips of her limbs as the continued stimulation proved itself to not be unwanted.
Her mind blanked as she underwent a violent, full body orgasm, every muscle in her body flexing and contracting as she pulled against everything the monster had with all of her might. It didn't budge, but she didn't care. It felt too good. She couldn't escape, but why did she want to escape, again?
Moments later, her body shook again, the harsh and fast fucking driving her body over the edge even more easily than it had the previous two times. This time, Twilight's mind didn't recover after being wiped clean again, and she didn't start thinking. The beast sensed this, and released her forelimbs.
Twilight immediately grasped for the tentacle slithering its way into her mouth, and began to tug on it. Her hooves slid over its slimy surface as she tried to stimulate it back, not caring, or noticing, that her coat was becoming matted and dirty with the otherworldly juices as the creature continued violently raping her, and she did her meagre best to pleasure it in return.
Several orgasms later, the tentacles began to become erratic, as the other party in this unequal bonding approached its release. The first time Twilight noticed this was when the thick, goopy liquid began to spew forth into her throat, filling her stomach and causing her to cough and choke as the tentacle pulled out, leaving what seemed like gallons of fluid to flow out of her now very empty and cold feeling mouth. It tasted salty, rough, and delicious.
Moments later, the other two erupted, filling every hole with the creature's seed, and bloating the purple librarian. She hit the ground with a soft squelch as her cum-soaked coat absorbed the impact, and her engorged belly caused her to roll over, unbalanced. She lay there gasping for what seemed like minutes, falling asleep contented in a pool of some alien creature's seed, a happy servant to its whims.
"Twilight? Me? Wake up, I'm sure I wasn't out this long. Ah, there you are!" Future Twilight beamed as Twilight awoke, surprisingly clean. "Gosh, that was fun, wasn't it. Anyway, you don't know how to do that, so take my diary, the spell is on the second last page. Don't read it! Make sure you give it back, too, I need it by tonight. I can feel the spell wearing off, now - don't forget, you need to go back and fix past-you so that it can fix past-past you! I think, anyway, I haven't had time to write the flowchart yet. Actually, can you do that, and just bring it with the diary?" said Future Twilight, before vanishing in a flash of light.
Twilight just sat there, with a stupid grin on her face, before opening up the diary and starting to learn the spell she'd need to fix her past self. She was going to enjoy this.