Silver rested beside Luna as she read and studied. They cuddled gently, but Silver did her best to not disturb the reading of her mentor. She had banished the extra parts long ago. She had no use for it, just yet.
A sudden knocking from the door drew both of their attentions. Luna frowned sharply. "Who is it? We are busy."
The door opened a crack and a lunar pegasus muzzle poked in, a fang visible. "Mistress, I apologize, but your sister has sent a missive."
Luna grunted softly. "We will remember this when she is enjoying her alone time." She rose up and strode towards the door. "Let me see."
A letter was passed through the door's narrow opening. "Here you are, mistress. I truly am sorry."
Luna smiled at the lunar pegasus. "You have done nothing wrong. In fact, come in."
The stallion stepped forward into the room, shuffling nervously. He wore the dark armor of a lunar guard, and looked like the others as a result. "How may I serve, mistress?"
Luna lifted the letter with her magic as she gestured to Silver. "Have you met Prince Silver Stars? I believe he entered office after you joined me, and you never had the chance to meet, personally."
Silver scrambled to her hooves and nodded at the guard. "A pleasure."
The guard dipped his head lower. "The pleasure is mine, mis-- uh..." He looked confused, eyes darting over her form. She was clearly not a prince.
Luna gently set a feathered wing on the guard's back. "Why so hesitant? Say hello to your prince. He is second only to me."
He coughed softly. "Oh, yes, of course. A pleasure, sir." He bowed low quickly. "However I can assist, please, inform me."
Luna developed a little smile. "You doubt? Silver Stars has experienced pain the likes of which would kill a lesser pony. He has faced an eldritch horror even I avoided. He won. He brought peace to the East. He survived countless assassination attempts. Once, he murdered one of his attackers for daring to assault him, slain in his powerful jaws. He is a warrior, a true warrior."
The guard looked a little more unhinged and terrified with every example of Silver's prowess. By the end, he was almost cowering. "I-is this true, your majesty? Is this one of your jests?"
Luna leaned in. "I haven't even described half of the scars he bears. But the most telling part... He loves, and he forgives. He would embrace a pony that just plunged a dagger into his heart, if the pony were truly repentant. He doesn't know how to hold a grudge, and while he may bear the marks of war, all he wants is peace."
Silver quirked a little smile, looking a bit uncomfortable herself. "I hope it never comes to that." She offered a hoof. "We can skip the stabbing part?"
The guard glanced between the grinning Luna and the friendly-seeming Silver. He swallowed heavily before he stepped in, and was drawn into a soft hug. He raised a trembling hoof and returned it, and some of the tension began to melt. Despite the horrible stories, she, er, he? They gave a warm and loving hug.
Luna's magic wrapped around them both and gently pulled them apart. "That's enough of that. Thank you, for the message. Tell me if anything equally important comes up."
The guard snapped a salute, and hurried from the room, quietly relieved to be away from the awkward situation. He shut the door quietly behind himself, giving Luna her privacy.
Silver gestured at the floating letter. "What did she say?"
Luna huffed softly and flipped it open, cracking the seal on it. "She reminds us that dinner is formal, and is to begin in a few hour's time." She waved a hoof at Silver, banishing the scuffs and ash gained in the scuffle outside. "You appear ready."
Silver returned the favor, wrapping Luna in magic and gently grooming her with it before taking to polishing her jewels and ensuring everything was straight. Luna let out a soft murmur as she settled before Silver's spellbook, resuming her study. "You are no professional groomer, Silver, but your eagerness is not remiss." She glanced at Silver out of the corner of an eye. "I will proudly enter with your work alone."
Luna softly tapped the book. "Is that enough time to try this?"
Silver flushed faintly. "I don't believe I'm in heat just yet, Luna."
Luna snorted softly. "We're to wait until the crucial moment to even practice? And don't call it a heat, my little barbarian." Luna rose up and her horn glimmered. The magic rushed down through her and she grunted as she grew what could only be described as a massive, black, horse cock.
Silver's eyes widened. "Luna! Please... It's to fuck me, not another of you. You're too large."
Luna leaned in. "That's what she said."
Silver blinked softly. Did Luna really just make that joke? "Yes, that is what she said. Now, seriously, smaller..."
Luna circled around Silver, letting her stiff new member bob gently with her motions. "Oh, you're not a little curious? To feel the full weight... and girth... of me?" She turned to Silver sharply, her tool swaying almost dangerously. "Behold it! It could be yours."
Silver flushed more and more at the display. Luna was being unashamedly forward. Silver hated the fact that it was working as well as it was. She did almost kind of want to interact with that big... massive thing. The naturally-sized member of Luna. "Luna... It won't help either of us if you hurt me with it." She leaned in and gently rubbed the edge of her muzzle along the side of that big horse cock. "You can't mount me with it. I forbid it."
Luna snorted gently, then smiled. "Very well. 'Tis your body, but if you won't let us mount you with it, what, pray tell, have you in mind?" She looked like she had several ideas, but she didn't say them, letting Silver decide.
Silver nuzzled down the length of the shaft, then nuzzled into the weighty orbs beneath and behind. They were covered in soft fur. Dark fur. She gently ran her tongue over it, tasting the newly forged balls. "I will show you what it's like to be pleased, as a stallion."
Luna tensed with pleasure, leaning back and letting out a slow sigh. "Oh yes, you're doing admirably. 'Twould be a shame if we made a mess after the effort to cleanse ourselves."
Silver withdrew suddenly, only to move in over Luna's cock, licking up the oozing trail of prefluids. "Luna."
"Mmm?"
"This is your new horn."
Luna snorted at that. "Is this a jest?"
Silver wrapped her lips around the tip, giving a single gentle suckle before drawing back. "I am not. You have to learn to think of it that way. This holds a powerful magic. The magic of foal making. You're going to need to channel through it heavily when it's time, with all the focus and determination of a city-destroying spell."
Luna tilted her head as she panted softly with pleasure. "How do we do this, when we are so distracted?"
Silver licked up and down the underside of her shaft, where the thick tube that would carry the seed rested. "I did not promise it would be simple. We are practicing now, so practice." She nuzzled back up to the head to find it was already sticky and wet with new leaks. She drank it up, then engulfed the flat head of Luna's member.
Luna grunted as she tried to capture the focus, to use her 'horn' as a true horn. Her hooves moved to Silver's head, pulling her down along the shaft gently as she felt it for the first time. That tense need. The male magic.
Silver took more and more of that massive girth into her snout, stretching her jaw and working her tongue over it. Luna's fluids were salty as they emerged. She ran her hooves carefully over Luna's new balls, feeling how they tensed and grew ready. She wouldn't have long to wait.
Luna took firm grip of that new need. She grabbed it, and she rode it. She pushed her magic powerfully through it, and her entire body began to sing with pleasure. The more she pushed, the better she felt, so she pushed more, and more and... She threw her head back with a sudden moan and her world was lost. She was hitting the peak. She was spilling into Silver's mouth, flooding it with her new seed as her own magic splashed out with it, filling her. Filling her willing mare. "Silver!"
Silver could not speak. She squealed as her mouth and throat exploded into tingles. She could feel her balls through her hooves. They were rock hard with tension, throbbing as they forced seed up into her firing shaft. The thick seed ran into her as she swallowed it down as quickly as she could, but it came so swiftly, some of it washed back up to coat her lips and run down her snout in a mess as she worked as hard as she could to keep up. Everywhere the seed touched felt a little tingly, and all too quickly, she slumped and collapsed, her belly full and her vision swimming.
Luna sank down on top of Silver and hugged her gently as she panted slowly, regaining the breath stolen from her. She shuddered as her new shaft suddenly drew back into herself. She had lost focus and expended energy too quickly. She started to say something, but it died in her mouth and she instead snuggled against Silver firmly. They didn't need words. She gently cleaned the mess she'd made of Silver with a twinkle of her magic before nuzzling the top of her head gently.
Silver slowly rolled over until they were belly-to-belly. "Luna."
Luna tilted her head tiredly. "Mmm?"
Silver kissed her on the nose. "How do you feel?"
Luna cracked a smile. "This is a practice I will not begrudge." She raised a hoof and set it under Silver's snout. "You, however, are still my stallion. Don't think this gets you out of your duties."
Silver suddenly burst into laughter. "Luna, seriously? After that, you needed to remind me I need to be on top too?"
Luna flushed faintly beneath her dark fur. "Yes! I'm not making you my mare, Silver. I, unlike my sister, appreciate a powerful stallion. You will still be my stallion, won't you?"
Silver slid up a little and kissed with Luna, pressing lips and closing her eyes. They hugged warmly, and stayed like that for a time. There were no misunderstandings between them.
Elsewhere, Twilight was taking care of her own business, unaware of the things Silver was getting up to, and fearing far worse than the truth of it.