You considered it a moment before you nodded. You told her that she'd get scholarly credit, it was only fair. You'd take your credit as the first human that did magic, and that was more than enough.

She smiled as she adjusted her glasses. "Excellent, then we should pro--"

Before that! We do need to tell the princesses.

"Hm?" She raised one of her huge brows. "I suppose that is the least disruptive path. Let's confer with them, then we can begin." She looked left and right. "I don't work at the castle, unlike some of my friends. Do you know where they typically are at this portion of the day?"

Celestia's voice broke the moment of awkward silence, "That will not be necessary." She stepped closer in her regal gait. "Do you really think this is possible?" Her eyes were on Moon. "A human trained in the art of magic? It seems unthinkable."

Moon pointed at your groin. "The modifications you've already performed have primed the event to occur. All that remains is training." She approached you and reached, touching your sheath through your clothes. "Much like our own horns, he has a long focusing device, itself inert and functionless."

Hey! Your 'horn' was far from functionless.

She cocked that thick brow. "As I was saying, it isn't the horn itself." That hoof trailed down to your balls. "The reservoir." She trailed up and back a bit. "The musculature needed to direct the flow. It will require discipline, but I feel confident all three components can grow more acclimated to the flow of magic."

Celestia considered this a moment before she dipped her head. "You understand this human is very precious to the kingdom."

Moon tapped at your groin. "Every precaution will be taken. The first matter will be restricting the flow, allowing the human to express magic in small amounts without harm."

Express? Wait...

Moon turned to you. "It will be an unfortunate side effect of how your horn is situated. I have doubts you will ever not have some link between magic use and sexual stimulation, but that is a small price to pay."

Celestia coughed softly into a hoof. "Yes, well... Please, proceed, but only so far and so fast as he allows. His comfort and safety are of top priority." She looked to you. "Do you consent to this?"

You did!

"Then I wish you both luck." She leaned in and kissed your cheek. "Thank you, for your work." She did not kiss Moon Dancer, but nodded at her. "I look forward to reading your report."

As she walked away, Moon turned her full attention on you. "First step, attenuation."

What?

"Limiting your flow." She reached and tapped your dangling balls. "We can't allow you to hurt yourself during this. A unicorn foal can sometimes have the same issue, being prone to wild surges that can hurt themselves and those around them. You are no different, and I suspect much the same precautions may prove effective, with some modifications."

Moon led you along at an energetic trot. While she did, you asked her if she was on the list. She looked over her shoulder at you. "Me? Seriously?" She turned back towards you. "While Applejack did speak highly of your skill and empathy, I am a scholar. I live to learn. Humph, me, a mother..." She pushed open a door with her magic and trotted past the guards. You hadn't noticed, but you had arrived in the research section.

Careful Study was there and lit up as she saw you. She looked at Moon curiously. "Hello, Moon Dancer. Have you reconsidered?"

Moon nodded at Careful. "Effective immediately, I am joining this operation. I've obtained permission to conduct an experiment on him." She pointed back at you.

Careful flinched. "W-what? Nopony asked me..."

Moon cocked that big brow of hers. "Is that required?"

Sensing hurt feelings, you assured Careful that she could take part.

Careful smiled a little. "I just want you to be safe." She came closer, glancing between you and Moon. "What do you plan to do?"

Moon Dancer began speaking in words you'd never heard of before. Something about an aetheric restriction ring?

Careful seemed to get it and galloped off, just to return with a small ring floating beside her.

Moon nodded at it. "Correct, but far too small. Do you have any larger?"

Careful shook her head. "I'm afraid not. Unicorn horns don't need much larger. Why?"

Moon took it with her magic and set it on a table. "This will require some time."

"For?"

Moon grunted softly, then tried to calm herself, perhaps reminding herself the lessons Twilight had given her. "It needs to be large enough to fit on his horn." She pointed back at you as she said it.

Careful blinked. "He do... oh." She blinked again. "Really?! No wonder... He doesn't narrow to a tip like a unicorn."

"Precisely." Moon nodded. "It needs to fit snugly, but without restricting blood-flow."

"I'll help." She moved to stand beside Moon. "I have his precise measurements."

"Excellent."

The two seemed to be getting along, which was nice. You had a curiosity though. Had your work through the day helped things? You asked Careful if she could check.

Careful blinked. "Already? I normally check once a day, but there's no harm in it." She drew the magical caliper from her coat. "You have to take off your pants first."

You dropped your trousers for the mare and she advanced on you. Your cock was peeking free of its home, stirred by all the conversation about it. Even as Careful gently hoofed at your balls to get a good measurement, you noticed Moon glanced towards you and your equipment a few times while being nominally occupied with the ring she planned to equip you with later.

Careful nodded with satisfaction. "Within 99% of original values! You must have had a wonderful day." She smiled up at you, large and sincere. "How do you feel?"

Tired. But in a different way.

Careful reached out to tap at a bruise. "What were you doing? Was it safe?"

Moon softly cleared her throat. "It is fortuitous that the subject is in prime condition, but we have another matter at hoof." She pointed at the ring. "If you're ready?"

Careful slipped the calipers away before turning back to Moon. "Right right, I'm coming." She trotted back over to the table and both their horns began to glow as they worked over that ring with combined unicorn might.

That left you there with your pants at your ankles. Easily fixed, at least. You pulled them back up, quietly hoping Sassy would come soon with your custom set. How long did it take to make clothes?

It didn't feel right leaving them, so you had a seat, and eventually nodded off.

You were awoken to the sensation of being rubbed along your sheath. You snapped open your eyes to see Careful was doing it with her magic. She saw you awake and smiled sheepishly. "It's time to put it on. Look." She pointed to Moon, who held an enlarged ring in her own magic. "I figured you would be better being handled by... somepony you knew..." She was blushing about it, but she had started it, and even resumed it. She stroked you up and down in slow motions.

It felt great, and you were rapidly filling from the attention. Your powerful pony prick soon jutted up proudly like the mighty horn it would soon be. Wait? When had your pants been lowered? You decided to assume the two unicorns watching you were more than capable of the trick.

Moon stepped up with a nod. "I presume this is his full size?" Careful nodded. "Excellent." She hovered over the ring and gently pressed it to your flat tip before wriggling it down, but it pulled at the skin a little and she stopped. "We require lubrication."

Careful coughed suddenly. She may have been a pony, but she was a human before that. The uses of 'lubrication' came to her quickly.

Moon cocked a brow from behind her glasses before grunting. "Tell me you have some in this lab."

"Actually..." Careful shook her head. "Not that I know of?" She glanced at Moon and you. "We do have some natural lubricants at hoof."

"Apply it immediately." Moon pointed at your twitching pole.

Careful's blush only grew worse. "What if it... over stimulates him?"

"Be careful until the ring is installed."

Careful hopped up beside you and nuzzled your cheek. "May I?" As if to show what she intended, she leaned in towards where the ring rested on the end of your cock and darted her tongue out.

She meant to get it down with some spit and care? Somehow, you'd heard of stranger... You told her it was alright and sat back.

Careful took the end of your cock in her magic and held it firmly as her tongue brushed along it. She lifted the ring away to get at the flesh underneath and slowly lowered it back down. It slid down slowly, inch by inch with her warm breath and saliva leading the way. It was working, and turning you on something fierce. Fatigue be damned, just let her keep going...

But then it stopped. She had reached the root of your spire, the ring installed just outside your sheath. "There." She sat up, still a dark red shade. "Did that hurt?"

That had been far from painful, you assured her.

Moon clopped a hoof on the ground. "Excellent. Now the true work begins. That ring works with both your 'horn' and your 'reservoir'. While it's on, you're, effectively, expended. You will not release sufficient quantities to successfully impregnate a mare, nor capably cast the impregnation spell. You will need to remove it before acting in that capacity. More important to us, you can now practice magic without hurting yourself until you learn how to properly measure and do it yourself without it."

So you could mess around with a mare just for fun?

Moon blinked at the idea as if it had never occurred to her. "That would be... logical." She cocked a brow at you. "Applejack was not wrong, you really do like mares. Why would you fornicate, knowing it would fail?"

Careful burst into laughter. "You do know that 'fornication' is quite pleasant, yes?"

Moon tilted her head a little. "Is it? Regardless, let's focus on the matter at hoof. We'll begin with a spell every unicorn foal learns, light."

She reached out and tapped your heavy balls. "You must envision your magic, here, glowing brightly, then allow it out, just a little, like a faucet barely turned on. Light has no specific thoughtforms or calculations. Proceed."

"You can do it!" cried Careful excitedly as she clopped her forehooves. "The first time I cast light was so amazing!"

Except she had a horn. You had a horse dick. Alright... You imagined your big balls filled with glowing seed, burning bright and focused on that vision.

You heard a gasp and looked down to see a faint glow coming from your balls, but it faded instantly. Moon shook her head. "In a unicorn, the reservoir is concealed, preventing the glow from being perceived until properly expressed. Ignore that and proceed."

"You did it," encouraged Careful. "You just have to finish it."

To avoid distractions, you kept your eyes open the next time. You focused on that glowing. How does one focus 'harder' on something? You weren't sure, but you tried to lock in the image of the glow your balls were putting off before, and it came back. Your magic, as it turned on, had a pale reddish color that grew a little richer as it developed.

Suddenly, you came. Magic/seed rushed up your shaft and squirted out in one meager splatter. The cum that had more oozed than fired spread over the tip of your tool, glowing brightly. That felt... really good, and it had worked!

Author's Note

https://www.surveymonkey.com/results/SM-5C69N3HN/

Your thoughts are quite clear. You want this. Before that, you want to throw it past the princesses. Moon Dancer, she's a nerd, but if she asks, you probably wouldn't say no, but you don't press the issue for the moment.

There is not even a tiny shred of doubt about this. Let the human horn augmentation proceed!

You just climaxed magic. That's progress!

Where are the choices? Here! https://www.surveymonkey.com/r/WFTCCWT

I'm going to let you guys fill in your survey questions directly this time. Please don't stop the commenting with your thoughts. I love reading those! They affect the story too, promise.