The train arrives at the Crystal Empire and Flash Sentry steps off with a few other ponies before he looks upon the vast kingdom made of crystals he was once posted at. "Long time no see." He said to himself as he got a nice view of it. He then remembers why he's here and not for a trip down memory lane. He's here because Princess Cadance has requested his help for something, only he wasn't told what that thing is. Flash took in a deep breath before he made his way towards the Crystal Empire's Castle where the guards escorted him towards a living room with a fireplace, a small table, and a couple of chairs. Those items weren't the only thing in the room as Princess Cadence herself was reading a book in that very room. "Princess Cadance, I'm here to answer your call." Flash said as he bow down to her.

"Thank you for coming," Cadance turned towards him and revealed she was wearing a form fitting white dress with her golden necklace and crown. She then gestured to a pair of seats facing each other. "Please, sit down." They moved over to the seats and sat facing one another, Cadance sitting in a manner that allowed Flash to see down her dress.

"What is this about, Princess?"

Cadance smiled at him, "I have need of your...expertise." That confused him. "You've managed to knock up not only my sister-in-law, but all her friends, the two other alicorn princesses and who knows who else." Flash was still confused, "how would you like to complete the set and knock up the last alicorn princess?"

Flash's eyes went wide, "Princess! Surely, you can't be serious."

"I'm very serious," Cadance smirked. "And please, don't call me Shirley." Flash frowned at her, as she sat back to try and show off more of her body. "What's the matter? Don't you find me attractive." Flash gulped as he remembered the many fantasies he had had of this very princess, even before Chrysalis blasted him with her spell. He hated to admit it, but Cadance had been his favourite masterbation image when he was younger.

"Of course I do. Honestly, if you were single I'd already be on you." Cadance smirked. "But you're married. And not just to anyone, but to my captain and the uncle of one of my future children. Why do you even want me to get your pregnant when you have him?"

Cadance sighed. "Believe me, I've tried." Flash raised an eyebrow at this. "Ever since Twilight and the others got pregnant, Shiny and I have been trying for a baby. But it hasn't happened."

"It will," Flash assured her.

"No, it won't. I secretly took a sample of Shining's sperm and had it tested. The chances of him impregnating me is very slim." Cadance told him before Flash frowned, "and I think I know why. In Shining's first year in the guard, he received an injury to his groin. It had him laid out for weeks, but it seemed to have had another effect."

"I see," Flash sighed. "Have you told Shining about this?"

"Of course not," Cadance shook his head. "Shining's always been Insecure about his manhood. If he found out he was infertile, I fear the shame my make him suicidal. And if I don't get pregnant soon, he might decide to test himself and discover it himself. That's why, I need your help."

Flash sat back and let this information sink in. Honestly, he could understand what Cadance was thinking. He had already proven more then once how good he was at repopulating the species. Her plan was a good one. She and Shining would have the child they want, Shining wouldn't need to know about his inability to breed and Flash would get to have a night of passion with his teenage crush. Everypony would win. However...

"I'm sorry princess," he stood up. "I understand where you're coming from, but I can't do this to the captain. If I did, your child would think it's mine's cousin. They'd always been playing together and I'd have to see Shining make a fool of himself thinking he's raising his own child. I respect him too much to let that happen."

Cadance sighed, but smiled. "You don't have to worry about that. I've already taken precautions to make sure the child is Shining's." This confused Flash, as a knock at the door caught their attention.

Cadance stepped over to it and opened it up to show a Crystal Unicorn mare. "Good evening, princess."

"Hello Ruby," Cadance smiled. "Do you have what I asked for?" The pony nodded and held up a bottle of silver liquid.

"I managed to get the hairs like you asked for and added them to the potion before the captain left." Cadance nodded and took the bottle, thanking the mare before closing the door and moving back over to Flash.

"What is that?" Flash asked, as Cadance stood over him.

"A potion I asked Zecora to make. If somepony drinks it, it'll temporarily rewrite their reproductive material to match that of whoever's DNA is mixed with the potion. I'm guessing you know whose DNA is inside it."

Flash took the potion and looked it over, "Shining's."

"Exactly. Drink that and for twelve hours, any child you father will be Shining's instead of yours. Don't think of what you're doing as betraying my husband. Think of it like...tagging in for him in a sport. The guards are all about working together towards a common goal. I'm sure if the roles were reversed, Shining would be willing to do it for your." She stepped away from him and walked towards another room. "My husband is out on an exercise and won't be back with his troops until tomorrow afternoon. That gives us all night to make a child before he gets back." She turned to smile at him, "still don't wanna do it?"

Flash thought it over and he knew this was wrong to take another's wife, but both Twilight devastated to find out she won't become an aunt. Not only that, Shining Armor would blame himself to find out he won't ever give Cadance a child. Flash let out a sigh before he gave an answer. "Okay, I'll do it your highness." Cadance smile as she handed him the potion before headed towards the door. "Let's go to your bedroom and we can get started." She smiled as she followed him out the door and to her bedroom.

Flash drink up the potent and was waiting for Cadance to come out of the bathroom because she said she wanted to change into something before they start. As he waited, Flash looked over himself and he wasn't any different. "Maybe the change is on the inside?" He wondered as he still felt a little uncomfortable about this. A part of him felt it was taboo to fuck another stallion's wife in the same bed they shared. He even thought his coat would turn white and had another thought that maybe Zecora's potion didn't work.

Cadance finally stepped out and Flash was greeted to the sight of her in a light blue silk nightgown. It was sheer, allowing him to see almost everything beneath it.

As he sat on the bed, he felt his pants growing tighter as Cadance got closer. As she did, she slowly and sensually began to undo the belt and slid it out of the gown. She threw it at Flash and he grabbed it, feeling the softness of the fabric as his imagination went into overdrive and he suddenly found himself picturing Cadance tied to the bed with this belt and helpless against whatever Flash chose to do to her.

Cadance then slowly slipped the gown off, first revealing her shoulders before letting it slide down her body to reveal what was underneath. And what she was wearing almost had Flash blowing his load right then and there.

She was wearing a three-piece lingerie set, which was almost completely transparent with the exception of the straps. It was the same light blue as her nightgown, matching her cutie mark beautiful. Her bra was holding up her large breasts and allowed Flash to see her dark pink nipples through the fabric, which were already starting to go hard and poke out. She was wearing a frilly garter belt around her beautiful hourglass waist, which had straps connecting to thigh-high stockings that stopped just below her cutie mark. Finally, she was wearing a pair of light blue panties that completed the image and made her look like something out of heaven itself.

"P-Princess... you look amazing." Flash told her in a nervous tone as his face was red as a tomato.

"Please Flash, call me Cadance." She told him as she got on his lap. "No change? Must be on the inside." He can tell that her tone was seducive as she started to kiss along his neck. Flash groan as she help them remove his jacket before she slowly took off his shirt and tank top to reveal his bare chest and muscular abs. "Just like his~." She then started to kiss his abs as her hands started to unbuckle his belt and unbutton his pants. After she pulled down his pants and underwear, she gasped in surprise when she got a good look of his cock. It was still 20 in long from the time he fucked the main six, the royal sisters, and Queen Chrysalis. "How did Twilight and her friends let you come here with this monster?!"

"Well, it's a long story." Flash told her as he rubbed the back of his head with a small blush. Cadance couldn't take her eyes off his cock as he looked bigger than Shining. She licked her lips before she began to lick his cock from the base to the tip. She then leaned forwards and gave the tip a quick kiss, getting a moan from Flash, then started licking it like it was the last popsicle in the freezer. "Oh fuck...Shining is a very lucky stallion." He moaned at her tongue skills.

"I'm glad you love it~." Cadance said before she pushed him on his back and put her cunt with very wet panties over his face. "But don't expect me to do all the work~." He smiled before he grabbed hold of her panties and slowly pulled them down to reveal her soaking wet cunt. Flash didn't want to disappoint her, so he took his muzzle deep within her cunt and lick every inch of her walls. "Aaahh~!!" She cried out when he began to eat her out.

Cadance then surprised him by sticking his whole cock down her throat. Flash moaned inside her cunt as she was able to deep throat him with ease before he continued to eat her out. The two of them were like this for what seems to be hours to them before she felt his cock throbbing in her throat. She didn't even slow down as she deep throated before with Shining Armor and wants to see if she can handle him when he cums. Flash soon unleashed his cum down her throat just as she came all over his muzzle. Cadance was drinking loads of his cum as she felt her lungs burn from the lack of oxygen but was not going to let his cock out of her mouth till she drink up every last drop.

Once his cock stopped, she let it out with a loud pop from her mouth before to her surprise, Flash quickly got her on her back to lay on the bed before he grabbed her bra and took it off with one pull. He then latched on to her right nipple while he played with her left breast by squeezing or pinching her nipple. Cadance let out a lustful moan as he was enjoying her breast as she felt his cock poke her below. She held his head close as he continued to suck on her milk before he quickly locked lips with her.

Cadance was surprised by his action before she quickly kissed back and tongue wrestled while they moan. She hugged him tight before he aimed his cock towards her cunt and gave one powerful thrust into her that caused her to moan so loud. "Fuck! You're...so...tight..." Flash grunted as he humps her. Cadance wrapped her legs around his waist as he thrusts into her rapidly.

"Oh Celestia!! Don't stop~!!" She told him as she brought her list up to his again and started making out while he thrust into her. Flash picked her up and continued to thrust into her rapidly while they make out. Flash then had her top half lay on her back while he thrusts into her harder. He didn't slow down as he pound into her even harder while he holds her legs up. Sounds of her moans and her flank being slapped with each thrust filled the room as she was enjoying his cock.

After almost thirty minutes of their constant pounding, and three orgasm for Cadance, the pair finally felt themselves hit their peak and they climaxed together. Cadance cried out and was glad she had soundproofed the room. That was the last thought before the mixture of pleasure and exhaustion overcame her and she blacked out.

Cadance's dreams was one she had had many times, of a great knight coming to free her from an evil villain and claiming her. But instead of her husband, who had always been the star of her wet dreams, it was Flash that burst into her tower room and took her.

This dream made her moan and as she faded out of it, she became more aware of her real body and realised her arms were up by the headboard and bond to it by something soft.

And as she became more aware, she realised something was touching her. A pair of lips were slowly travelling up her stocking clad legs. And when she opened her eyes, she saw Flash was awake and doing just that.

Her movement made Flash aware of her awakening. He looked up at her and smiled, Cadance smiling back as an idea popped into her mind. Shining didn't enjoy roleplay, but maybe he did.

"Oh," she moaned, "Who are you? What are you doing here? Why am I tied to the bed?"

Flash seemed to instantly realise what she was getting at and started playing along. "You've been teasing me and the rest of the guards for too long. Your husband kicked me out of the force when he caught me checking out your sweet ass. Now I'm gonna get what I lost my job over."

Cadance pretended to gasp, "Please no. I can't be untrue to my husband."

"Oh, you'll soon change your tune." He said before he ground hold of her hips and begin to thrust into her. Cadance couldn't help but let out a loud moan as he thrust into her really rough. Flash then leaned forward and nibbled on her neck as he continued to thrust. "Ah! I bet your husband never fuck you like this before~?!" He asked before giving her breasts a few good smacks.

"Ah! N-No he...ah!..ne-never did!" Cadance answered through her moans of both pain and pleasure. Flash was only getting rougher as he pinched both her nipples and pulled on them hard. Her eyes rolled in the back of her head as he continues to plow her. "Pl-Please...don't...aahhh...stop~!!"

"So, you love how I fuck you better than your husband?" Flash asked as he slapped her flank hard to leave a handprint where her cutie mark is while he thrusts into her more.

"Much better~!!" Cadance shouted as her tongue started to hang out of her mouth. "He never gave me this much pleasure before!! Fuck me harder~!!" Flash granted her wish as he thrust into her even more while he sucked on her breasts. The wet sounds of his thrust mixed in with her moans filled the room as he took her.

"I-If you want me to c-cum in you, call me your master and say you're the princess of lust!!" Flash told her as she felt his cock throbbing in her womb.

"Please!! Pl-Please master, c-cum inside the princess of lust!! I'm your princess of lust~!!" Cadance begged. Flash smiled before unleashing his cum into her womb yet again and bloated her belly even more. The fun didn't end there, however. As after only an hour's rest, Flash was ready for another go. He untied Cadance and the pair were at it once again, with Flash lifting them into the air and performing a technique he and Rainbow perfected.

He flew up with Cadance on his cock and stopped mid air, allowing Cadance to almost fly off his dick until gravity stopped her right at the tip and pulled her down onto him hard and fast. They did this several times and Cadance was in heaven.

She had a feeling that potion had an added benefit, allowing Flash quick recovery. It only took him a little bit of rest after that event to be at it again, then again and again. All throughout the night, the pair were at it like rabbits and Flash's balls never seemed to empty.

Her belly bloated from the amount of cum getting poured into her and impregnating her. Once they finally stopped, after what was probably their tenth go, Flash was resting on her as his cock was still inside her. Cadance never felt so much pleasure before, even when Shining Armor took her in bed. She smiled as she cuddled him close and the two of them fell to sleep.

The next morning, the two of them were still asleep until Flash woke up and remember what happened last night. He gently pulled out of Cadance before hitting the shower. After a few minutes, Cadance slowly woke up to find Flash putting on his clothes and looked ready to head out. "Leaving already?" She asked him.

"So sorry your highness, but I'm a little concerned with Twilight and the others." Flash told her. "What if they need me and the babies are coming? I want to be there for them and well--" He was silenced when she used her magic to keep his mouth shut. Flash looked at her and saw that she had a warm smile on her face.

"It's okay Flash, I understand." She told him. "And you can call me Cadance. Just have yourself some breakfast before you leave and tell Twilight I said hi and I'm proud of her, along with her friends." Flash smiled before he took the handle of the door. "And one more. For what it's worth, I think you make a good father and a great husband to them. You really convinced me last night." Flash chuckled a little before he gave a smile back to her.

"Thank you, and I hope you give birth to a great kid." Flash told her before he opened the door and went on his way. Once Flash was gone, Cadance sighed as she let herself continue to lay upon the bed.

She could still feel the enormous amount of cum flowing through her body, trying to get out. But she wouldn't let it. She grabbed a pillow and pushed it under her, keeping her body folded so her cunt remained pointed to the ceiling and the cum pooled down into her womb. As she patted her slightly swollen belly, she realised Flash had probably shot more cum inside then in one night then Shining had throughout their entire relationship.

A knock on the door caught her attention and she pulled her blanket over her body, "yes?"

"Princess," it was Ruby, "can I come in?"

"Of course," Cadance nodded as Ruby stepped into the room. The crystal unicorn looked her over and smiled.

"I can see you've had quite the fun night."

"It was wonderful," Cadance told her. "And hopefully, it will lead to the results I'm hoping for."

"So do I, princess. So do it."

Cadance nodded. "Thank you again, for getting the hairs I needed. If you hadn't, Flash never would have agreed to it." Ruby nodded as Cadance's curiosity got the better of her. "So, what did Shining do when you got the hairs. Did he flinch or anything?"

"No. He was too busy marching towards the border with his troops. None of them would notice a few hairs flying off of him. A quick snip with magic and they were mine."

Cadance nodded, then heard what she said as her eyes went wide. "Snip. You cut the hairs off him?" Ruby nodded, looking confused.

"That's what you told me to do. Get a few hairs and put them in the potion."

"But I didn't mean cut them off. I needed you to pull them out, hair follicle included."

"Why? He would have noticed if I did that." Cadance wanted to yell at her, but realised she wouldn't know. She and the rest of the Crystal Ponies were from a time before science really advanced. They wouldn't know hair itself didn't have any DNA. But this meant the potion hadn't had any DNA to rewrite Flash's genes with. That meant...Flash had been shooting his own loads into her all night.

Cadance removed the blanket and looked down at her stomach, now realising that it could possibly be growing Flash's child within it instead of her husband's. She wanted to be scared, but for some reason she was actually kind of...happy. She didn't know why, but the thought of having Flash's child alongside the rest of the alicorn princesses just felt right to her.

She sighed, a smile appearing on her lips. There was a chance she hadn't been impregnated, but she knew in her heart she was. She was going to have Flash's baby and that was alright with her. Though a part of her also wondered if she could convince Flash to give her a second baby later on, then a third, forth and maybe fifth.

Back in Ponyville, within the castle of friendship, Applejack and Fluttershy had finally come up with one or two mares for Flash to have fun with. Fluttershy thought that Dr. Fauna and Zecora for Flash to fuck and Applejack thinks her old friend Rara would be perfect. Twilight caring a list of mares for Flash as she walked down a hallway before she stopped and heard moaning coming from the room with the pool. She open the door and saw Spike on top of Smolder as he was thrusting into her cunt. "Oh fuck Spike, take me harder~!" Smolder mona as he slapped her ass.

"Celestia, I love how hot and tight you are Smolder~!" Spike told her as he continue to thrust into her on the edge of the pool. The two of them were so focused on their little fuck session, that they didn't notice a flash from a camera flash on them. Twilight quickly close the door with a camera in her hands as she looked at the picture of her son and his mate.

"I'm so proud of you, Spike." Twilight said as she continued her way down the hall and couldn't wait for Flash to get home.

Author's Note

I had help making this one by https://www.fimfiction.net/user/284583/Banshee531