Rainbow Dash's Royal Duty

by Rainbow Chaser

Rating: mature
Tags: Princess Cadance, Rainbow Dash, Sex, Anthro, Slice of Life, My Little Pony: Friendship is Magic
Length: 2321

Rainbow Dash tests out a strange potion for Twilight, and the results set forth a chain of events no pony really saw coming.

Rainbow Dash decides to test out a potion that Twilight has been working on for a while. The effects are supposed to control a mare's desires when in heat. However this potion has a different effect on her. An effect which Princess Cadence offers to help her relieve.

(This is a commission done for Mr. Ghostman if you like this story and would like me to write you one, just PM me. I don't charge for my commissions X3)

(Contains: Futa, Cum Inflation, Thigh Fucking, and light musk)

Published 2016-03-25 23:50:01 UTC
Last updated 2016-03-25 23:50:01 UTC

Taste The Rainbow, Love The Rainbow, Fuck The Rainbow

Taste The Rainbow, Love The Rainbow, Fuck The Rainbow

"Rainbow Dash will you please take this seriously! If something goes wrong, the results could be disastrous." Twilight said as she mixed a few vials of liquid together. Rainbow Dash laid on the couch in Twilight's lab tossing her ball in the air.

"Oh come on Twilight, how bad could it be? I've tested a lot of your potions before and nothing bad has ever happened. What makes this any different?" Twilight looked at Rainbow and huffed.

"Because I'm experimenting with a potion recipie that could possibly help mares in heat. Cadence gave it to me. For all we know, this could either make you so sterile you'll never have a foal, or it could turn you into such a horny nympho that you'll start humping anything that moves." She explained as she finished her unknown concoction. "It's finished."

"Finally! Can we get this over with? I have to go and practice my flying stunts for the wonderbolts show on Saturday!" Rainbow said as she sprung up from the couch, walking over and picking up the bottle. "So am I supposed to drink this, or what?" She asked.

"For full effect, yes. But only take a sip please... There's no knowing would happen if you consumed the whole bot- HOLY FUCKING CELESTIA RAINBOW DASH DO YOU EVER LISTEN?!" She shouted as Rainbow placed the empty bottle on the table giggling.

"Oh lighten up Twilight! I was thirsty! Besides, that was really tasty!" She said licking her lips. "It almost tastes like Pinkie's home made cherry berry punch!"

"Ugh Rainbow, I swear one, of these days, your wrecklessness is going to get you into trouble." Twilight said with a bit of frustration. "Moving on then... Do you feel anything?" Rainbow looked at her.

"I don't feel a thing, Twilight I think this potion is a dud. I feel no chan-" As Rainbow Dash spoke, she doubled over holding her stomach. She started to feel hot and sweaty as her crotch started tingling. Her body shook and spasmed for a few moments before she stood back up.

"Woah... That was weird... Twilight?" Twilight was silent. She was staring at Rainbow in a look of shock mixed with arousal. "Yo, Twilight? Anyone home?" Then she noticed exactly what Twilight was staring at. It was her crotch. She looked in the mirror and gasped. "WOAH!"

Hanging between her legs, was a large flaccid cock, looking to be about six inches in its current state. Underneath that was a large plump set of testicles. She brought her hand down to poke them and shuddered as she felt her new member start to harden.

"What the?! I'm a stallion now?!" She took a closer look and saw that her pussy was still there, sitting right underneath her large ballsack.

She blushed hard, as her cock spurted out a glob of precum from its tip. "Woah!" She bit her lip. She needed to get out of there and fast. She rose up and flew out the window, leaving a sexually frustrated Twilight behind staring in awe as her well endowed friend flew away.

"SPIKE! IM TAKING A LONG BUBBLE BATH, DON'T BOTHER ME FOR THE EVENING!" She shouted as she ran to the bathroom, a wet trail of sweet smelling liquid left behind.

Meanwhile, Rainbow Dash had landed on a near by cloud above the outskirts of Ponyville. She laid back, her new massive cock standing straight up at sixteen inches in length.

"How can I fly when I have this thing sticking out all the time?" She reached out and touched her hand to her newly formed shaft, gently running it up and down its silky smooth surface, feeling every vein and bump she saw. Then she moved her hand down to her testicles and squeezed one of her succulent orbs, giving out a light moan as precum started to ooze from the tip, making her cock slippery and wet.

"Haaah... This f-feels so.... Awesome.... Hnnh...." She started to stroke her cock in a steady motion as her eyes rolled into the back of her head in ecstasy. She put her other hand up her shirt and fondled her breast as she jerked her cock, pinching her nipple and biting her lip to keep from screaming out in pleasure.

After a little while, she took her shirt and bra off, letting the cool air hit her nipples causing them to become erect. She decided to try a trick she read about one night when she was looking for something to masturbate to. She came across a picture of a Pegasus stallion humping a cloud as if it were a sexdoll. Rainbow licked her lips, as she turned over. "This is going to be so awesome!" She said to herself as she shoved her massive member into the cloud.

It felt a little weird at first, but oddly satisfying like sitting on the bubble jets in a hot tub. An act in which she was all too familiar with when she visited the spa with rarity.

After catching her breath, she started to slowly hump the cloud she had been laying on. It felt cool and breezy, but warm at the same time. Rainbow started thrusting faster and faster, surprised to see that it actually works. She started squeezing her breasts and her breath became ragged as she came closer and closer to release. However.... Nothing happened.

"Oh come on! Why can't I just blow my load and be rid of this already?!" She moaned, still humping the cloud.

"Wait... Princess Cadence gave Twilight the recipe for that potion... Maybe she has an antidote as well!" She stopped thrusting and stood up. But something felt odd. She looked down and gasped. Her cock had grown bigger by a few extra inches at least. There was no way she could hide it. She shook her hips and felt her nuts sloshing with cum. She felt them and realized they had swollen up as well. There was no telling what would happen if they got any bigger.

"How am I going to hide this while I'm flying?" She asked herself. But then she finally figured it out. With enough maneuvering, she was able to tuck her cock in between her breasts held snug there by the middle of her bra. Then she put her shirt back on. No pony would notice anything off about her if she flew fast enough. She opened her wings and immediately took off, flying towards the crystal empire, hoping that Cadence really did have a solution.

A few hours later, Rainbow Dash had landed on the balcony just outside of Cadence's throne room, and not a moment too soon. Her shirt was completely soaking with precum from her cock. Every movement she made while flying caused her turgid member to spurt a glob of sticky sweet nectar all over her breasts. Not that she minded of course.

She walked into the throne room and looked around. "Hello? Princess Cadence? Shining Armor? Anyone?" Rainbow called out. She walked through the halls and looked around. "Wow... Not much security around...." She noted out loud. It has been a while since the last major threat in equestria, so it came as a bit of surprise to see a lax in security around here.

As she passed the bedroom she heard a noise. It almost sounded like someone was hurt... She moved closer ready to kick the door down, but stopped as her jaw dropped.

"Mmmm yes fuck me! Fuck me shiny! Fuck me like the horny little slut I am!" Princess Cadence was laying on her back, panting heavily and squeezing her massive breasts as she thrusted a large dildo in and out of her.

The aroma of her feminine musk hit Rainbow dash in the face as her cock sprang free from between her breasts. A large blush formed on her cheeks as she breathed in, her cock growing harder as her balls practically ached to be emptied. As she kept breathing in the princess's amazing musk, she failed to see Cadence had stopped masturbating and was looking right at her.

"Who's there? Why are you spying on me!" Cadence shouted as she got up and opened the door. Only to be greeted by a well endowed and horny Rainbow Dash. "Rainbow Dash?... What are you doing here?" She asked as she licked her lips. "Mmmm where did you get that?" She stared at the massive rod of flesh poking out at her.

"U-uh... Th-that's why I'm h-here princess..." Rainbow began. "Twilight had me test a new potion you gave her and I took too much, and well... I grew this. Only I can't get rid of it, or get it to go down... I've tried masturbating, but it only makes it worse." Cadence smirked.

"Well of course, because you need to find a willing partner in order to release yourself... Didn't twilight read the full notes I gave her? She usually reads everything." She said giggling. Rainbow whimpered.

"So basically I need to fuck someone in order to get rid of this dick?" She asked curiously. Cadence nodded.

"But only a willing partner... Since Shining Armor is away, I suppose I can help you." Rainbow almost fainted either from shock, or from how hard her cock grew as the princess spoke.

"Y-y-you'd be willing to fuck me? But won't shining armor be mad?" Cadence laughed.

"Of course not! Well, he might be mad that he wasn't here to watch, but even though we are married, we tend to spend a lot of time away from each other because of royal business." She explained. "So, we tend to be a bit open about our relationship. We've even gone so far as to have massive orgies in the throne room from time to time. Also, on a few separate occasions I've invited a few mares to come assist me in pleasing my husband. Or vice versa." She said proudly.

Rainbow's jaw dropped again as her cock started twitching, spurting precum on the floor at Cadence's feet."W-wow..." She said still in shock.

Cadence smiled and took hold of Rainbow's hand. "Now... Let's get a bit more comfortable shall we?" She said as she led Rainbow to the bed.

Rainbow Dash stripped all of her clothes off and sat on the edge of the bed, her cock twitching in anticipation as Cadence turned and sat, positioning Rainbow's cock right between her ass cheeks.

Cadence started grinding her hips as she used her butt to massage Rainbow's massive cock, giggling as she felt each throb between her soft toned cheeks. Soon the room began to fill with the smell of sweat and sex as Cadence continued to give Rainbow Dash her Royal Buttjob.

When they were both wet enough, Cadence stood. As did Rainbow Dash. Rainbow stood behind the princess and started humping her. Cadence looked down and moaned as she saw Rainbow's hot wet rod sliding between her thighs, feeling every ridge and veiny bump against her pussy. "Mmmm Rainbow no more teasing me!" Cadence said as she laid on the bed, ass up. "Fuck me with your giant dick!"

Rainbow Dash wasted no time in getting on the bed and positioning herself just behind cadence. She pushed her cock right into Cadence's aching pussy and moaned loudly as she felt the princess's warm velvety walls wrapped around her cock. "Holy fuck this is awesome!" She leaned in and squeezed Cadence's massive breasts as she started furiously humping the princess.

Cadence let her tongue roll out as she moaned, feeling every inch of Rainbow's cock fill her. She bucked her hips back and squealed as she felt the tip hit her G spot over and over. Rainbow continued moaning and humping as she felt herself getting closer and closer to sweet release. She moaned even louder as she felt Cadence's pussy flex and pulse around Rainbow's cock, milking her.

"Oh fuck! I'm gonna cum! Cadence I'm cumming!!!" Rainbow screamed as she thrusted hard into the princess.

"Do it Rainbow! Do it! Fill me with your cum! Fill me!" She screamed out as she came. Rainbow Dash gave one last hard thrust and moaned loudly, as her cock squirted glob after glob of cum into her pussy. Soon, Cadence felt her belly start to expand as she continued to be filled with cum.

Rainbow's orgasm lasted five whole minutes until it died down. She pulled out of Cadence with a wet schlick and collapsed on the bed next to her. Cadence rolled over and rubbed her swollen belly filled to the brim with Rainbow's seed. "Mmmm I really needed that..."

"That...was...AWESOME!" Rainbow said as she panted. She looked down to see that her dick had finally disappeared. "Aww man, I was starting to enjoy that thing." She frowned.

"I think I know how to get more." Cadence said with a smirk.

Meanwhile

"Hey Twilight?.... Twilight where are you?... I have a letter from Cadence asking you to make more of that weird potion!" Spike called out as he searched for Twilight.

He knocked on the bathroom door. "Twilight Cadence sent another letter! Do you want to read it?" He asked.

"Uh n-no that's okay spike! I'm just gonna finish my bath!" Twilight said with an urgent squeak. Spike opened the door and walked in.

"I'll just leave this he-" his voice fell silent as he stared at twilight, her cheeks were flushed and her hands were moving very frantically under the water. When she saw him she jumped.

"SPIKE WHAT THE FUCK!" She said as she covered herself. Spike however smirked.

"Jeeze Twilight, you couldn't at least let me join?"

THE END

Author's Note

I hope you enjoy this story, I really really enjoyed writing it. It took a while, but I hope it was worth the wait. :raritystarry: