Ascension Detention

"Potion!?" Twilight gasped. She looked at the two cups in front of her. Celestia hadn't touched either of them. "What kind of potion?" she asked. The chair around her began to slowly get bigger, as did the table in front of her and the princesses, as did everything. She was shrinking.

"Well, that answers that," Luna said. Twilight tried climb down off of her chair, but quickly found that the drop had become much too high for her now. She called to her magic to teleport herself. But the spell fizzled.

"It's a shrinking potion, Twilight," Celestia said, "With just a splash of magic inhibition." Twilight looked visibly scared. "Don't worry. It's only temporary." Luna poured two more potions. One into a pink cup, and the other into a blue cup.

"Now then, you have a choice to make," Luna said.

"I'm not drinking any more potions!" Twilight said.

"Oh, these aren't for you," Luna explained. "You get to decide which of us will take the more... involved role with your ascension."

"Ascension?" Twilight asked.

"Yes Twilight. You are to be reborn as a Princess, like us," Celestia explained. "But it's an involved process for all of us. And you may choose which of us will have the primary role." Twilight looked back and forth between them and wavered.

"It's alright, Twilight. You needn't fret over our feelings. We will both be happy with whichever choice you make," Luna said, taking the pink cup. Celestia took the blue one.

"Okay," Twilight said nervously, "Celestia, I guess."

"Hmf," Celestia vocalized. Neither surprised or expected by Twilight's answer. "I suppose you always did see me in a motherly way." Celestia and Luna exchanged cups. Celestia now had the pink one, and Luna had the blue one. "Cheers," she said, clicking her glass to Luna's before they each drank their potions. In a few moments after settling into her chair, the effect's of Luna's potion became apparent. Twilight gasped. A massive penis began to slowly sprout from the front of Luna's marehood. It was blue, mottled with blotches of black, much like the rest of her rump.

"Hmmm," Luna moaned as it reached full size.

"Princess Luna!?" Twilight cried out in shock, shifting away on her own chair. She was now barely bigger than a foal. She looked over at Princess Celestia, fearing a similar development. Celestia just sat there, visually unchanged, with a dull grin and half-lidded eyes. "Celestia?"

"Mmm. My potion just made me a bit more... flexible," she said.

"I don't understand! What is going on!?"

"We are ready to begin," Luna said, rising from her seat. Twilight felt herself surrounded by Luna's blue magic, levitating her up onto the table, which was now a dizzying height for her.

"Begin what?" Twilight asked, stranded on the table. Either she was too small to be heard, or they were simply ignoring her. Celestia climbed onto the edge of the bed and flagged her tail, fully revealing her marehood. Twilight could only watch as Luna mounted her sister from behind, bringing the tip her cock to her entrance. The bead of precum at the tip smeared against the wetness of Celestia's vagina, letting her penetrate her with ease.

With a few small thrusts, Luna was able to get most of her shaft into Celestia. Twilight blushed and looked away. It didn't feel right to watch two ponies in such an intimate act. Let alone the fact that it was Princess Celestia. Let alone the fact that it was with her sister. The purpose of all of it eluded her. But even with her eyes averted, her ears could still hear the sounds of the two princesses in ecstasy. The table below her grew larger as she continued to shrink.

"Oh Luna, I- I'm- I'm cumming!" Celestia moaned.  Luna quickened her pace as her sister brought her to orgasm with her futa cock making wet, slapping sounds against Celestia's gushing pussy.

"Ngh, I'm nearly there," Luna grunted.

"Okay. Get her," Celestia said.

"Get her?" Twilight thought. She turned around just in time to see Luna slip her penis from her sister and walk over to the table. For Twilight, the ground thundered with each step from the giant pony. Twilight was now no bigger than a pencil eraser. She glowed blue as Luna took her in her magic, levitating her as she carried her towards the bed. Luna hovered the tiny Twilight in front of Celestia's face.

"Twilight, this next part might seem scary," Celestia said softly, "But I want you to trust me. Everything is going to be okay." The blue magic around her whisked her away, down along Celestia's body, past her tail, towards Luna. Luna brought the tiny Twilight to the tip of her penis, just at the opening. She winced as she used her magic to push Twilight into the tip.

Twilight felt herself snugged very tightly in the tip of Luna's urethra, with just her head sticking out of the end. Her entire blue penis throbbed around her in time with Luna's heartbeat. Twilight turned and looked ahead as Luna moved forward. She was rushed forward along with her cock towards Celestia's rapidly-approaching vagina. In an instant, Twilight felt the pressure of Celestia's wet flesh against her head, and then everything went dark as she slipped inside her love tunnel once more.

Twilight felt tremendous acceleration, lurching forwards and backwards again in rapid succession. The insides of Celestia's vagina whipped by her, riding inside the tip of Luna's penis. Luna tried her best to go easy. She had waited as long as she could, until she was ready to cum before inserting Twilight. But the feeling of the tiny pony in the tip of her penis was very uncomfortable for her, and it was making it somewhat difficult for her to climax. Celestia sensed her concern, and likewise did not want to prolong Twilight's ride.

"Luna, please cum inside me," Celestia said, trying her hoof at talking dirty, "I need you to cum inside me. Please, I need my sister to fill me with her cum." Luna grunted and felt her need boiling up again. Inside, Twilight felt herself moving faster, and more violently as Luna's thrusts became more frantic. She felt Luna's cock swelling around her, growing harder and thinker. She was getting close. "Yes Luna, cum inside me! Push it in! Push it all the way in!"

Luna pushed forward, deeper and harder this time. Twilight felt herself pressed hard against Celestia's innermost barrier. The cervix, normally a tight, unyielding ring of muscle, was made lax by Celestia's potion. With a few more determined pushes, Luna forced her cock through the tight opening. Inside at last, Luna's cock flared wide around Twilight. She could feel it throb. She knew what was going to happen next.

"I'm cumming!" Luna shouted, slamming her hips against Celestia's, pushing as deep as she could. Luna's balls tightened and she felt the first bout rush up her shaft. Twilight felt and enormous pressure suddenly behind her. But it wasn't enough to dislodge her. Luna's first rope was trapped inside her dick. "YEAAARRGGG!" Luna let out a feral cry in intense pain at the blockage in her penis. Luna's cock throbbed again. The second bout of cum was more than enough now. Twilight was positively launched into Celestia's yawning womb.

She landed onto the soft, warm lining of Celestia's uterus, followed by a torrent of Luna's cum. She tried to scramble for high ground as the massive blue cock above her continued to pump load after load of hot semen. Twilight ran around the growing pool towards the throbbing penis as it slowly retreated. She scrambled towards the cervix, Celestia's yellow magic on it her only source of light. But it snapped shut as Luna's dick slid out, and the light vanished. She struggled to pry it open with her hooves. Her magic was still unavailable to her. It was no use. She was trapped. She gave up and slid down the interior in the dark.

The pool at her hooves slowly grew more shallow, and the space around her began to close in on her. Or rather, she was beginning to grow. The effects of the spell began to wear off.

Luna pulled her cock from Celestia's pussy with a wet 'plop'. Luna smirked and watched it relax from being so stretched, and regain its original shape and size. Luna's cock, now spent, shrank and retreated into its sheath, before vanishing all together as the potion's effect wore off.

However, Celestia's ordeal was only just beginning. She groaned as she felt Twilight regaining her original size within her, stretching her belly.

Twilight felt her whole world move as Celestia shifted her body to stand. She moved sluggishly with the extra weight of the mare inside her belly. She slowly climbed back onto the bed, laying on her side, rubbing her swollen tummy .

"You look so beautiful like this, Tia," Luna said, laying beside her. Luna's hoof joined Tia's, rubbing her stretched abdomen.

"Luna, I'm so tired," Celestia said.

"Sleep now, sister. You need your rest for the journey ahead." Luna leaned he head against Celestia's stomach. She could feel Twilight kicking and struggling, her hooves trying to pry at her cervix to break free. But it was no use. The way was shut securely. Celestia could only giggle at the sensations of her moving inside her.

"Tickles," Celestia said.

"I suggest you get some sleep too, Twilight." Inside, Twilight was curled up in a ball in the tight confines. She could hear Luna's voice, a bit muffled. Twilight was exhausted. The entire ordeal had worn her out. She hadn't the strength to fight any longer. It was warm, and strangely comfortable. She could hear the deep thumping of Celestia's heart all around her. It was easy for her to close her eyes and fall asleep.