"So what, we just...drink them?" Bon-Bon asked, eyeing the pink 'Estrus Initializer' potion held in her hoof. She and Lyra now lay on the bed, holding their appropriate potions, both feeling a bit nervous now. This was a giant step they were taking after all, and despite both wanting it fully, they knew there was no going back after. A foal was a huge, permanent investment after all; of time, responsibility, love, and Bits all.

"Yeah, the instructions said to just drink the whole thing. I guess the magical ingredients do everything else." Lyra responded, before looking at the small vial in her hoof.

"So...?" Bon-Bon asked, holding her own vial and rolling it softly between her hooves, "We sure about this?"

"Yes. I undoubtedly am. If you're ready, let's do this. Let's make a foal." Lyra said, meeting eyes with Bon-Bon and getting a nod, before pulling the cork out of her potion.

Bon-Bon thought for a moment, before nodding again. She then followed suit, glancing down at the thick pink sludge inside it. She could swear it bubbled.

"To our future, and our future foal. Cheers!" Lyra said as she gently tinked her bottle to Bon-Bon's, before tossing it back. Instantly her senses were assaulted with an intensely bitter, spicy mixture that tasted kind-of like rotten licorice, but she forced herself to choke it down. It burned the whole way down her throat. "Bleh! Gah, that was awful!" she exclaimed, quickly grabbing a nearby glass of water and chugging it down.

Now even more nervous, Bon-Bon sipped her own potion, before downing it. She found that her potion tasted like strong cinnamon mixed with something exceptionally sweet, as well as a twinge of carrot and carbonation in it.

Within seconds after drinking it however, Bon-Bon started to feel...warm. Very warm. She found she was starting to sweat as she felt the heat spread throughout her whole body, before focusing strongly in her lower belly. She moaned as she felt a prickling heat starting there, and knew exactly what it was, having felt the same thing many times throughout the years since she was a young filly.

Bon-Bon was, undoubtedly, going into heat.

In winter.

Meanwhile, Lyra started feeling...strange as she finished drinking the potion. She felt that just above her pussy was getting very warm and...felt like it was stretching, expanding. As she looked down, she saw a lump starting to grow out of her crotch, and only growing larger by the second. Well that was something new.

Lyra simply watched and waited for the weird feelings to end; finding the stretching to feel strange and mildly uncomfortable but not painful, though oddly kind-of arousing. After a while, Lyra started feeling a tingling inside her head, briefly growing dizzy and her vision swimming before stabilizing again. The potion's document hadn't said anything about that.

When the dizziness passed, Lyra looked down at her crotch for the first time since the potion started its work and found quite the results; within thirty seconds she saw she'd grown a pair of rather large testicles, as well as finding a minty-green-furred sheath now between her legs, the sensations of stretching still present as the potion gently melded the inner flesh, making Lyra's crotch feel rather warm and tingly as thousands of new nerve endings formed with each passing second.

In an instant Lyra was engulfed by the lightly-musky scent of a mare in heat surrounding her and making her new, now-fully-formed equipment quickly start growing to full attention. "O-Oh..." Lyra stammered out distractedly, that scent of Bon-Bon's heat awakening something within her that had apparently had come with the penis, that very distinct odor setting her new stallion instincts ablaze; a desire to mount Bon-Bon almost overpowering all other thoughts, as well as the weird feeling of her penis slipping from her sheath and growing erect for the first time. "Dang...guess your potion worked too, huh?"

"Yeah...it did. I'm definitely in a bad heat. Dang this burning's—Oh. Oh wow!" Bon-Bon started to complain, only to exclaim as she looked underneath Lyra's barrel and saw what she now had, more than a little lust in her voice as she started to feel the burn in her belly again; the burn of estrus burning brighter, the sight and scent of Lyra's now fully erect cock quickly setting her breeding instincts alight.

It was quite big, for sure looking out of place on any smaller mare, let alone Lyra.

"Uh, I don't know if it's supposed to be this...big." Lyra said as she studied her new member, laying on her back and prodding at her sizable new cock, hoping something didn't go wrong with the potion. As she gave it a gentle rub, she shuddered from the new, weird, but quite pleasurable, sensation as she did, her hips humping upwards at the touch, a foreign instinct to Lyra.

Bon-Bon, meanwhile, looked over her mare's new light-pink-skinned length, finding it gently mottled from base to glans, her equally-large balls furred in a thinner minty-green hair than her coat. "Wow, that's certainly a new part of you..." Bon-Bon said, finding that Lyra's 'package' wasn't overly huge but was certainly very much in the upper range of even an Earth-Pony stallion's size, noting that it actually looked a bit bigger than their shared dildo in both length and girth. That meant it was probably around fourteen inches long and four in circumference, her unflared glans at least five. Earth Ponies were well known for having thick cocks and flares, and Lyra's was right alongside them despite her not being an Earth Pony, as well as longer than most to boot.

"Yep...I haven't always had it y'know..." Lyra quipped.

"Not...now, Lyra. Not when I'm this horny..."

Lyra simply chuckled in response.

"Dang, you are hung!" Bon-Bon continued, looking over the length and feeling her powerful breeding instincts spurring her into getting this stallion atop her, "I love it!"

Despite liking the praise, Lyra couldn't help but wonder something. "Hm...I wonder why the potion made the cock I grew so big..." Lyra pondered, before remembering one of Zecora's rhymes from when she was describing the blue potion; 'Keep in mind that your partner’s needs it will surmise, and will quite possibly give the resulting growth more than normal a bigger size'. As the scent of her fertile wife-to-be set her mind aglow with lust, she gave a sexy grin, "Oh. Right. It's juuuuust the right size for you...we have just what we need for us to have a foal..."

"S-says you! It's not going inside of you after all! That thing's a sexy beast!" Bon-Bon exclaimed, but her tone wasn't fearful or even reticent despite her words. Instead, it was filled with desire, and Lyra stood from the bed as Bon-Bon mounted it instead, her back legs off of it and spread while her front half remained on; presenting herself to be mounted. As Lyra stepped behind her, she could see that a steady stream of her mate's thick, slightly-yellow-tinted breeding fluids were flowing already.

Bon-Bon hated being in heat, as did virtually every mare in Equestria, and the thought of intentionally having started it seemed almost ludicrous to her. The constant burning, the uncomfortable sensitivity and arousal; not being able to keep your mind off of finding a stallion and having him rut a foal into you, or a mare to help keep it under control. But, for the first time in her life, she embraced her heat for what it truly was: a way for her to have a foal with the pony she loved most.

As Lyra saw her fiancee's clit wink when she raised and flagged her tail over her back, she felt as though red-hot hooks of lust were driven into her, dragging her towards Bon-Bon. She suddenly started to quickly trail nibbles and kisses down her neck, to her chest, to her belly. Lyra debated on teasing her more, but decided against it. She too knew what it's like to have a horrible heat, and wouldn't wish it on anypony.

Instead, Lyra then licked between her teats on her way up to Bon-Bon's literally soaked marehood, immediately getting to work giving rough licks against it, feeling her clit wink against her nose on reflex as Lyra licked only harder.

As Bon-Bon winked again, Lyra found herself with her muzzle buried into that soaking wet crotch, sniffing deeply, taking in and saturating her mind with her musky, fertile scent. Before she knew it she was licking deeper into her lover, hearing Bon-Bon giving out quiet gasps and whinnies of pleasure as she lapped deeply, taking Bon-Bon into her every sense: she heard her sounds of pleasure, felt her shivering in pleasure and her wet walls squeezing on her tongue, smelled her fertile scent, tasted her thick, musky fluid on her tongue, and her whole vision was taken up by her mate's beige-colored rear. The virtual flood of her lightly-sweet and distinctly feminine-tasting fluids and moans ftom her told Lyra she must be doing perfectly.

Bon-Bon couldn't help but squirm in pleasure as she lay there, being licked by Lyra once more, her clit constantly winking in invitation against her muzzle. Bon-Bon could feel nothing but white-hot bliss rolling through her with every movement of Lyra's tongue, her well-lubed and heat-sensitive passage letting Lyra's tongue slide effortlessly into her. She wanted to say something, but her mouth couldn't do anything but produce moans of pleasure or ragged pants.

Bon-Bon's whole body was thrumming with pleasure the same it did every time Lyra ate her out while she was in estrus, but this time felt more...special. Knowing she would soon be receiving a thick cock, the cock of Lyra herself, and her virile seed along with it made her lust burn even brighter, as did the scent of a stallion's musk.

After only a minute of Lyra alternately licking her clit, as well as deep inside of her, Bon-Bon's hind legs started trembling as it always did when she was getting close. Her constant winking and small squirts of fluids made Lyra's now fully-hardened penis smack against her barrel at the stimulation, leaving a string of pre between her barrel and flare.

Lyra was amazed she had as much control over herself as she did; a newfound instinct was making her need to mount the ripe mare, to breed her, but she fought to hold on. As she felt her lover trembling, she focused her licks directly onto Bon-Bon's rapidly-winking nub and gently suckled on it, earning a quiet squeal as that finally set her over.

"L-LYRA-AAAAAAAAH!" Bon-Bon shouted as her resistant body caved in to the over-stimulation, with her letting out a moan of pure bliss as her back arched up, trying to keep Lyra's muzzle pressed into her slit as she painted it yellowish once more, grinding her cum into Lyra's muzzle fur and feeling intense pulses of pleasure rolling throughout her body.

As she came, Bon-Bon found some semblance of relief, feeling her passage clenching rapidly on Lyra's tongue and soothing her sexual needs for the moment. As she came down fully moments later, however, she felt the burn still in her belly, though less intense now. She knew the only way to truly put it out though, and looked eagerly forward to it.

"So, how do we wanna do this?" Lyra asked, pulling her glistening muzzle from between Bon-Bon's legs after she'd licked as much of the flavorful fluids from her fragrant folds that she could find, virtually ready to pounce her as she was.

"Like this is fine to start, though I heard that using dragon-style* is best when trying to conceive. It lets the stallion's member and seed get and stay very deep in the mare's pussy and womb..." Bon-Bon said, lidding her eyes, her tail swishing rapidly in her sexual frustration, "...but however you want to start is fine too. All I know is that I need you inside me now!"

Nodding, feeling her own needs boil over, Lyra leapt up and mounted Bon-Bon, a hoof landing to either side of her. It felt oddly natural, her attributing that to the potion.

Bon-Bon moaned at the feeling of Lyra's underside rubbing against her croup, that instinctive tell of being mounted making her clit wink rapidly, making her fluids drool out and onto the floor. As she felt Lyra's flare tapping her rump, her back arched a little higher and her back legs spread wider on instinct, giving her 'stallion' the best possible target. "C'mon...c'mon..." she whimpered to herself as much as Lyra, each miss making her wince, before finally Lyra got an idea.

Reaching down with her magic, Lyra grasped her penis with it, gasping as she squeezed a little too tight and felt a surge of pleasure roll through her, a thick blob of pre-cum landing on Bon-Bon's left stifle. Without any further context, Lyra seeked until she found her flat head pressed to Bon-Bon's winking entrance, both ponies moaning at first contact. "D-Do it!" Bon-Bon called out, and Lyra complied instantly on instinct.

Instantly Lyra's flare was surrounded with the hot, squeezing, moist insides of her fiancee as she pressed forth, slowly burying herself on reflex up to the medial ring inside the hot, fertile mare pussy. She let out a gasp at the sensations, holding stark still as she got the odd thought that this felt very similar to when she was mounted by Bon-Bon with the strap-on, but that this was what the dildo itself would feel if it was flesh. "Oh....b-buuuuck..." Lyra moaned out, holding Bon-Bon's sides tighter as she felt her passage clenching down desperately on it, wringing it tightly as though it would leave her forever if she let loose for even a moment.

Lyra grasped Bon-Bon's sides tightly at the internal assault on her stallionhood, it feeling heavenly having that nearly hot, ribbed, velveteen passage rubbing over her shaft, so wet she slid in easily while being actively aided by Bon-Bon's contractions. "Holy buck...you really want it don't you...you want me to cum deep in you, huh?" Lyra asked, feeling Bon-Bon's clit winking along every inch she slid into her mate's breeding passage, only to receive a needy whine from Bon-Bon, as well as an especially tight squeeze inside her.

Bon-Bon meanwhile felt a wonderful stretching not unlike that of their shared toy inside of her, but it was bigger, thicker, and was pulsing and warm. Alive. It felt far, far better than it had any right to, especially with her in heat. She felt herself being filled full of her first actual cock ever, never showing interest in actual stallions, always having her eyes on Lyra since she'd met her as a foal. She'd considered taking a stallion into her only for them to stud and impregnate her, but never had she had sex with a flesh-and-blood stallionhood....until now. That wondrous stretching, combined with the scent of her Lyra's feminine lust and stallion musk, as well as knowing Lyra, a mare, was putting her dick inside of her, made the situation beyond erotic.

Lyra knew this was Bon-Bon's first time with a stallion too, and was making every effort to make it just like her actual first time, which she'd also shared with her.

"Lyra...fuck me..." Bon-Bon intensely whispered out, already pushing back on her, and both moaning as that slight pressure forced Lyra's medial ring in, another intense surge of sensations making Lyra pant already as she felt that most sensitive band enter, a second later feeling Bon-Bon's pussy lips against her balls. Apparently, Lyra had finally hilted her.

Intense clenches from Bon-Bon along Lyra's whole length only spurred her on, and Lyra's hips were already moving without her consent, sliding her in and out of her mate's slippery mare-hole.

"A-As you wish, my love." Lyra said, and almost instantly started to slowly move her hips, the first humps being very unsteady and jerky. Soon though, she found a natural rhythm, her new stallion mindset helping her out in that matter as she then started to slowly take Bon-Bon, before remembering she was in heat and likely needed something more than gentle loving. She quickly started to move her hips faster, embracing her instincts and grunting softly each time she entered again fully, each time she pulled out a momentary tease of the wonderful, tight heat she knew Bon-Bon's body would soon offer her again. Lyra kissed down her love's whole muzzle and neck while she humped, her entire body awash in the pleasure of breeding a fertile mare.

Bon-Bon, meanwhile, felt that each of Lyra's deep humps brought her thick glans to mash up against her deepest barrier, making her breeding instincts go wild at that sensation, shuddering deeply and clamping down hard each time she felt it. The tingles going through her from the kisses, nips and licks on her muzzle, neck and crest only made her pleasure increase more, her fluids flowing freely and each thrust making a wet squelch go through the room, each hilt making a wet slap sound out as those heavy, seed-ladened balls slapped against her teats and stifles.

"F-fuck yeah! Fuck a foal into me!" Bon-Bon half-shouted, losing control of her speech as she was drunk on pleasure and relief, high on the sensations of being spread so wide by cock, a real, virile stallion cock, in her estrus. She felt like she was floating, Lyra's medial ring constantly hitting her clit, and finally she could take no more. Bon-Bon cried out as Lyra hilted once more, feeling a sheer wave of bliss burst through her as she came intensely, her whole body twitching and trying to work the stallion inside of her of his seed.

"Y-Yeah, cum for me Bonny...cum around my stallion cock..." Lyra said as she found she was able to resist the urge to cum rather easily despite the intense ripples along her cock that trapped her inside her climaxing mare, though she chalked it up to the potion's work rather than her own willpower; she knew those milking sensations would likely make a natural stallion dump his nuts in seconds.

Bon-Bon's passage meanwhile started to milk Lyra's pulsing rod on reflex as another nerve-wracking wave of orgasmic pleasure flooded through her, her left leg twitching rapidly as her third climax hit her very hard, making her arch her back and feeling Lyra's cock slide just a little deeper as a result. She gushed more of her mare-cum out onto Lyra's crotch and the bed, saturating them in her pleasure. As her contractions slowed moments later, Lyra then started rocking her hips, before developing the same rutting rhythm she was at before.

"S-still?!" Bon-Bon moaned in disbelief, feeling more intense sensations going through her, leaving her drooling on the mattress. As the humps suddenly stopped and Lyra pulled out, she was confused, before feeling herself being rolled onto her side and felt a weight and warmth grasping her from behind, Lyra bringing her into a spooning position. As she felt that same lovely, hard warmth slide between her legs from behind, Bon-Bon moaned out as she felt that same flare push between her slit again and deep into her pussy, delirious with pleasure now as Lyra continued to fuck her silly, giggling and shuddering uncontrollably as she bit her forehoof to cope. "Y-yeah, fuck me more...I know you can go faster!"

The position shift allowed Lyra to enter Bon-Bon deeper and from a different angle than before, the new sensations only confusing her mare mind more, but at the same time feeling very, very nice. She kept the thrusts smooth and varied, each time feeling her ring entering that lovely slick flesh, with each entry of it into Bon-Bon's tightness sending a surge of deep pleasure through Lyra's body, not unlike having her clit rubbed as a mare. She kept humping as deeply and rapidly as she could, before she felt a tightness forming in her pelvis, it feeling much like when, as a mare, she was—

"B-Bon-Bon, I feel like I'm going to c-cum soon!" Lyra groaned out as she felt her flare swelling up thick, assuring her seed went and stayed deep inside her fertile mare's passage and womb, giving it the best possible chance of taking root and growing a foal. Her humps grew shallow and rapid, her body's instinct taking over for her at this most important of times. "L-last c-chance to b-back out!" Lyra warned despite keeping her humps up just as fast, feeling her glans stretching her to-be broodmare's inmost passage tighter around her. She felt a ring extremely deep within her passage, undoubtedly Bon-Bon’s relaxed cervix, pressing against her flat tip.

Bon-Bon considered the warning for only a moment, before rolling over onto her back with Lyra's help, the latter continuing thrusting deep, clearly unable to stop for any longer. Bon-Bon looked deep into her love's, her to-be foal's sire's, eyes as she wrapped her back legs around her croup, and this forced Lyra's thrusts to be shorter and stay deeper, constantly hitting her cervix with each hilting and letting Bon-Bon enjoy being fully filled. Keeping as much of her lover's cock inside as possible for her muscles to milk, her clit to wink along as she neared her own limit. "I'm ready, Lyra! Make me, make us, a mother!" she said, before letting out a choked-off moan as she herself came again, ramming her muzzle against Lyra's in a rough, feral kiss.

Lyra let out a muffled cry of her own into her fiancee's mouth as she felt Bon-Bon clamp down on her again extremely tightly and rapidly, feeling a rippling motion from her base to flared tip, wetness splashing onto her crotch as Bon-Bon clearly squirted. Lyra's hips slammed forward a final time as all four of Bon-Bon's legs formed a death-grip on her croup and back, keeping her hilted fully and her chest pressed against her own. Her flare was pressed to Bon-Bon's womb's relaxed entrance, the legs around her croup ensuring she was unable to pull out even if she wanted to...not that she did. That cry was interrupted with the welcomed invasion of Bon-Bon's tongue against her own, and, after throbbing a few times, each one becoming harder, she finally felt that pressure in her pelvis burst.

Both cried out as Lyra felt her seed burst forth, sheer pleasure rolling through her body as she was kept fully encased in Bon-Bon's foal-passage, pressed right against her cervix and planting her seed directly into her fertile womb in thick globs. She'd never felt something like this before, never feeling such an intense, pulsating orgasm, nor feeling utterly satisfied and as though she'd accomplished her life's goal as she pulsed her gift of life into Bon-Bon's foal-oven. In a way, she had accomplished one of them; having a foal.

Lyra also felt her own pussy contracting and winking, her back legs trembling as she oozed her own mare-gasm onto the floor and side of the bed. She trembled as she experienced two orgasm at once, her mind overwhelmed as both sets of instincts and genitals were conflicted at the feeling of the other's pulsing. Lyra, however, was having the time of her life.

Bon-Bon meanwhile felt as a thick, hot warmth shot deep into her belly, making her cry out in agonizing pleasure as her body milked more and more of Lyra's virile seed into itself, bringing more and more cum to pool into her womb and keeping it there as her position on her back and Lyra's thick flare prevented anything from escaping.

Finally, after nearly a minute of pure bliss for both, Bon-Bon's belly slightly swollen with the unnaturally huge load she'd taken, Lyra and Bon-Bon both relaxed. Both were panting to catch their breath after their most intense shared orgasm ever, having gazed into each others' eyes the entire time.

Bon-Bon felt completely filled with a sticky warmth deep in her lower belly, indeed the first time she'd ever taken a stallion's seed. The fact that it was Lyra's own brand of foal-cream only made it that much more intensely pleasing.

After resting for a while, now slowly making out in their afterglow, their lips eventually separated and Lyra looked down into Bon-Bon's eyes, seeing a new sparkle in them as tears formed. "Is something wrong?" Lyra asked, still holding deep into her lover's filled passage as Bon-Bon's legs around her croup had only partially loosened during her orgasm, feeling as a wet warmth pushed back against her flare. She'd certainly filled her up well and knew that, with her ovulating multiple times right now, the odds of this pregnancy not taking were slim. She hoped Bon-Bon wasn't having second thoughts, now that everything was done.

"N-No..." Bon-Bon whimpered, burying her muzzle into Lyra's, still feeling spread fully by her lover's staff, her heat completely extinguished now from the virile semen completely filling her entire tract, "no, t-this is...th-this is the best Hearth's Warming gift...ever. Th-thank you so much for making this possible!"

Lyra nuzzled into Bon-Bon's mane, shuddering as she still gripped Lyra's spent cock inside of her, not wanting to let go. Eventually however, her softened stallionhood slid out, making Bon-Bon whimper in disappointment as it disappeared into Lyra's sheath once more.

As she felt a wetness against her belly, Lyra rolled off of Bon-Bon so she could place her hoof against her leaking vulva, preventing any more seed from escaping. "Can't have any of that coming out. It all needs to stay inside you so it can make our foal..." Lyra whispered, earning a small moan from Bon-Bon at her hoof's contact, before levitating and sliding into her mare's seed-filled pussy a flared buttplug she'd bought as an improvised dam to keep everything inside, earning an even deeper moan as Bon-Bon felt the sperm compact more inside her. "...and gift number four."

"This...can't be the last time we use those kinds of potions." Lyra said, giving Bon-Bon's scalp gentle kisses as she still held her tight, "...or do this. That penis potion..." she trailed off, actively drooling as she remembered how good what they'd just done felt.

"No...no it can't," Bon-Bon replied, "I've never felt so...close to you as I do now and..." Bon-Bon's voice stopped in its tracks as the implications once more came to her. "...we're going to have a foal!" Her voice was soft, that rough breeding leaving her exhausted, unable to fully express her joy beyond a near-whisper.

"Faust willing, yes we will." Lyra responded, smiling as she softly rubbed her fiancee's lightly-swollen lower belly, knowing it'd likely reach that size and much, much larger in the coming months; "A little piece of you and me joining together to make a new life inside you. A foal for us to love and teach...and maybe even more than one in the future..."

"Mmmm...I'm going to be...a mom..." Bon-Bon said weakly, and before Lyra knew it, she was asleep in her hooves, a dream already forming of what their foals could look like. Lyra meanwhile continued to gently pet her love's mane, smiling softly at what would likely come of this.

"Happy Hearth's Warming, my love. Mother-to-be of my foal." Lyra whispered, smiling. "Best. Hearth's Warming. Ever." Moments later she too joined Bon-Bon in the Realm of Dreams, cuddling close to her wife, her love, dreaming her own little dream of their foal-to-be as the fire crackled softly, before eventually, it too was exhausted.

Author's Note

* - Dragon-style is my version of the MLP equivalent position of missionary.

Whew, just made it to post this on Christmas! As this was kind-of rushed, there will likely be some wonky stuff I'll have to work out later. I plan on having one more 'epilogue' chapter to this, but I'll post that later once it's done.

Have a Merry Christmas all, or a Happy Hearth's Warming!