Twilight walked over the next door clockwise, to the one marked with a cloud and a thunderbolt. As she put her hand on the stone to feed the magical lock her own power and lust, she took a deep breath and holding it until the door was open. Despite her body needing it, and she just desiring it, Rainbow was intense, and Twilight needed to level herself beforehand.

After the first step into the chamber, everything became a blur. She had to spread her wing to stop what would have been and endless fall. The air currents around her quickly began to push and pull her to one side after another, almost randomly changing directions in an instant. But Twilight knew it wasn't random, it was a pattern so fast and so vast, it as just impossible for most ponies to understand.

She shut her eyes and embraced herself, hugging her shoulder and pressing her arms against her breasts as well as crossing her legs in a new attempt to level herself. She released more of her power, dropping the many limitations she usually had to put on her strength and senses in order to interact with her mortal ponies on the surface. When Twilight opened her eyes, the blurring storm around her wasn't no more. The gale winds became a caressing breeze over her fur, which she welcomed.

Under her hoovering feet there was a line of light and electricity, thick as a road. It extended and split ahead of her, turning into a web of lightning that extended where only her divine senses could really see. She put her index finger on her lips, slightly licking it. Her lust this time came from the surging pride of seeing her work's success. A net of magical energy that spread over across the entire world, reaching inwards to hidden dimensions and outwards to the cosmos. The entirety of the realm she ruled powered by her grander design.

And it just felt too good to look at, knowing it was all hers.

After perfecting the magical absorption with Applejack, Twilight immediately got to work into manipulating so much power. She needed to know how much she could take and, more importantly, command. She still thought like a mortal back then, so she was content with just working Equestria's ley lines, taking power from them in a more refined way than just absorbing their product. But then, she remembered her friends. Applejack was still 'normal' enough to be around Ponyville, but Twilight knew they were far beyond any mortal creature. The idea of only them surviving the rest of their friends was too much to handle. That's when Rainb --

A streak of lightning surged from a ley line behind Twilight and tackled her, turning the world around her into a blur again as she was pushed into another ley line, being carried by the current of sheer power. A pair of hands reached around and across her chest and abdomen, as she felt a toner body pressed on her back. The touch was electric, as well as the air around her. Twilight felt every inch of her body being tickled by the buzzing magic.

For about a nanosecond, Twilight considered opening her wings and releasing herself. For her it wouldn't take more strain than pushing off the bed's covers. But the hand on her abdomen slid down to her penis, stroking her hard as the other hand began to roughly squeeze and massage her breast. That was all the motivation she needed to let herself be taken and carried, as the body pressed on her back began to rub itself between her wings and over her ass.

She hung out her tongue, tasting the electricity as the strokes on her body became rougher and faster. In a blink of an eye, Twilight was mindlessly bucking her hips, feeling the other body behind her moving along, as she was salivating, lactating and precuming. The hand on her breast slid up, pushing a pair of fingers between her lips, which she gladly began to suckle. If the air tasted like electricity, the fingers outright electrocuted her, making her orgasm violently, thrashing and convulsing.

Twilight's wild reaction caused her and her partner to fall down from the ley lines, crashing hard on a terrain made of solid rock. Not that it could harm her or her friend. Neither of them could really be harmed in a way that mattered.

She tried to turn around, still worn from the sudden surge of stimuli, climax and impact. But when she got on her four before getting up, a pair of clawed hands held onto her hips. She could feel the slim and strong fingers sinking in her soft flesh as a hard shaft slid up and down between her cheeks, rubbing just above her anus. It didn't take long before a wet tip started to push into her, stretching her as it made its way in. Twilight took note of the size, clearly bigger than her own penis, as the hands holding over her hips slid up to hold her sides. The tip met her prostate, pressing it down and making her leak again.

The penis inside her began to move, going all the way back to her anus and then ramming all the way in, reaching deeper with each thrust that also became more vigorous as they went on. Twilight let her upper half fall over, rubbing her breasts and face against the stone from the movements behind her hips. She was making a puddle of her fluids on the floor between her knees, trembling heavily. The only thing keeping her up where the hands on her sides that slightly caressed their claws closer to her abdomen, and her own need for more.

With some effort, Twilight planted her hands on the floor and slowly pushed herself up on her four. Twilight her felt partner slid their hands up her body, making her also feel the feathers rustling her as both hands grabbed her breasts. Her partner's body wasn't just electrical, but also hot, turning the air around them light and the stone ground to redden. Twilight was sweating profusely as her partner pressed themselves on her back again, heating her up further.

She reached back to feel her partner, rubbing the feathers that adorned their arms.

"Rainbow..." Twilight whispered.

"Blitz." He finished for her. She nodded in understanding as she let him do as he please with her body.

His groin met her ass, squeezing it as the full length of his penis was inside her. Rainbow Blitz reached deeper with each thrust, making a bulge in lower abdomen. Twilight's sweat began to evaporate as the heat kept rising, especially when his feathered arms slid up and down her body. Suddenly, she felt a rush of heat spreading inside her, overfilling her and making the bulge in her abdomen to grow. Rainbow stood still for almost a full second as she felt the cum getting up to her stomach. It didn't last, though, as he began to move inside her again, this time even more vigorously.

She couldn't hold on much longer releasing another large amount of cum that made a puddle under her body, before collapsing on her expanded belly. His body was a surge of heat and electricity pressed against her back, groping her breasts, making them leak and penetrating her deeper insides. There was a new surge of heat inside her, as she felt it now in her middle and upper torso.

Twilight's body was being filled with cum as she marinated in a puddle of her own fluids over nigh-molten rock, orgasming over and over. Each time he came and made Twilight's body fuller, Rainbow picked up the pace, becoming more aggressive with his movements and caressing of her, also making her cum faster. Twilight stopped feeling the buildup, as her climax became a constant buzzing of her overheated body, filled by and releasing constant streams of cum.

They ended up covered by a thick screen of steam composed of Twilight's own fluids. She could feel Rainbow inhaling the fumes behind her head, feeling hotter from the thought of what were they breathing.

Surrounded by red and white-hot stone, Twilight felt the massive penis finally pulling off her anus, leaving it gaping and leaking out overheated cum that just melted the rock between her legs. She was immobile and spent, not even sure if she could move anymore. But that didn't seem to bother Rainbow, who took her by her shoulders and turned her around. The motion made her aware of how much fuller her body was. Not just her bloated belly as it started, but it looked as if she had gained weight.

Twilight's breasts had grown from a modest to an abundant size. Even her areolas and nipples became wider alongside. Her abdomen, while not massive, now was a round belly, followed by wider hips and a heavier ass. The size spread to her arms and legs, making them twice as wide as she was used to. With great effort, she touched her face, feeling it softer and rounder. In fact, her entire body was softer and rounder as a result of Rainbow Blitz filling her over and over. And she loved every little sensation of it.

In front of her, Rainbow was standing on his knees between her open legs, masturbating to the sign. Like that, Twilight could appreciate better his body. Like Applejack, he had become more than a mortal body, so as time went on, he lost any attachment to it. Instead of a pegasus girl, Rainbow preferred to become more toned and thin build so he could make himself a projectile. The wide wingspan on his back became a colorful row of feather on his arms, ended in clawed hands. Same of his legs, which became muscular with the constant exercise or running forever to generate the magic of the planet.

Twilight couldn't help but notice how much animalistic he became in the last centuries. It was as if his one-track mind only became more focused like a ray of light becomes a laser through a ruby. He was still coherent and had an identity -as fluid as it was, changing from Dash to Blitz periodically-, so she could trust her friend wasn't lost to his newfound power. Another flaring success by applying what she learned with Applejack.

Thinking about how much she made out of Rainbow, and how much the world improved by her hand, made Twilight feel invigorated again without the need of a spell to replenish herself. It did help that Rainbow, no matter the gender, always presented himself as this slim marvel of anatomy and aerodynamics. Twilight could admire him masturbating for years. Specially if the object of his pleasure was herself. He seemed to love what he did to her body, exhausting it and then overfilling it with his own fluids.

Twilight reached down from her face to her breasts, massaging them in wide circles to emphasize their new size, lactating a heavier flow. Rainbow also picked up the pace, massaging his defined abs and pecs while keeping his other hand on his penis, making a sound of rustling feather from both limbs. Twilight reached down, confirming her penis was also larger as the rest of her inflated body. They both kept pleasuring themselves in front of each other, surrounded by the endless stone and ley lines carrying magical energy above them.

Always the rusher, Rainbow couldn't keep himself on his knees and dived down, hugging Twilight's wide frame, and burying his face between her breasts. She hugged back, caressing the back of his head with a hand, and down his back with the other. It didn't last long for him to start rocking his hips, rubbing his long penis on Twilight's wide one. The mix of fur and feathers, of rubbing and caressing made it so there was steam and static around them again.

They came together, slowly leaking from between their pressed bodies down to the floor. They kept at it until they were rubbing on each other over large pool of their own cum they could bathe in.

Being bigger, Twilight didn't have much trouble holding Rainbow, grabbing his arms, and sitting him on her belly. She was licking her lips, looking down at his groin. Not at his penis, still hard despite the marathonic session, but to what was behind it. As lubed as they both were, Twilight didn't have trouble sliding him down, until his ass gently touched her erect penis.

Rainbow looked straight into her eyes, also licking his lips before freeing himself from her grasp. He leaned down, putting his open palms on her wet areolas as he lifted his ass, rubbing himself on her as he slowly lowered it over her penis. Twilight couldn't help but gasp when a small spark of electricity pinched her tip, followed by his hot anus pushing it down. It was clear the inside of Rainbow's was as charged and heated as the outside.

As he massaged Twilight's breasts, he started to move up and down over her penis, pushing harder each time until his tight anus began to open and crowned her tip. As she expected, it felt like taking lava as she felt herself slowly sliding up inside him. She reached for his ass, but he kept pressing her down by her breasts and keeping her straight against the floor. So instead, she settled for caressing his open thighs.

When his anus finally reached down to the base of her penis, he clenched hard over it. Twilight started to moan louder as he followed it by squeezing her breasts, making a flow of milk to come out. He then sat straight, pushing his weight over her penis, and smeared the milk over his abs, then up to his pecs, making his toned body shine. Twilight could only stare with her hands resting over his thighs when he started to masturbate again over her.

Rainbow started to move up and down, making her fattened body giggle as he picked up the speed. Rainbow was so his tight, his insides were outright milking her penis, driving her over to the climax, and barely holding back. Rainbow was still stroking himself as he moved, reaching up to his chest and playing with his nipples. Unlike her, he gladly released a generous amount of cum over her body, spread over her large breasts moving up and down from his movements over her hips.

Despite really ~~wanting~~ needing to taste it, Twilight didn't scoop the cum with her hands or extended her tongue down them. Instead, she kept holding onto his thighs as she held herself back. Rainbow's moans indicated he was close to a second discharge that promptly bather her upper body with more overheated cum. It felt like small flames licking and running down her body, along her sweat. It made her feel wet and hot all over.

They kept at it for a while, each time covering more of Twilight with cum as Rainbow's anus kept holding hard from her penis. They were on a puddle again, him cumming more than the heat from their bodies could evaporate. Until Twilight finally felt him slowing down.

That's when Twilight leaned up and closed her hands on his waist, holding his lower body against her groin. She began to move, not with the buzzing speed he's been using on her all this time, but with seismic trusts that outright cracked the stone beneath them. Rainbow could only grab his face as he felt Twilight ramming herself inside him, reaching deep and rubbing hard. It made him cum without control, but as soon it touched her body, it evaporated with a hiss. It made her smile openly, hanging her tongue to a side and showing her teeth now jagged and pointed.

While she enjoyed letting her friend do with her as he pleased, Twilight couldn't help but also need to take him too. He already had his fun with her, now it was her turn.

She restrained her perception of time again. The world around her picked up the speed, turning the almost imperceptible breeze back to the gale winds that were almost strong enough to make her feel it. But more importantly, Rainbow Blitz turned into a blur sitting on top of him. Twilight moaned again as his anus turned into a constant vibration around her penis. He kept cumming, a full load almost every tenth of a second that only evaporated over her body. She greedily inhaled the fumes, laughing as a pair of blurred hands reached down to her wrist. The touch was merely a vibration.

Twilight salivated, imagining what was it like for him. Every moment of her thrusting her hips would feel like hours of a penis slowly making its way inside him and then slowly retreating.

Feeling such control over someone as powerful as Rainbow was enough for Twilight. She stopped holding back and began to move harder and faster. Slowly, she caught up to him, returning to the same time perception and making it so he wasn't just a vibrating blur for her. Rainbow looked spent and in trance, as if he had been having sex for days without a pause. Which was probably how the relatively few minutes felt to him.

Sliding her hands up his side, Twilight pulled him against her soft and plump body. She cooed while caressing his back again, calming him down as she finally started to cum inside him. The softer stream was a far cry from the quick and violent orgasms they have been sharing, instead slowly pouring herself inside him. She could feel his toned abs giving way to a small bump, and then a belly. Unlike Twilight, Rainbow's body was more resistant to change, he only bloated instead of gaining it as weight like she did.

Nonetheless, Rainbow was full with an abdomen almost as large of the rest of his torso. He burped a bit of cum that reached all the way through before gently falling asleep on Twilight's arms. She kept caressing him, cleaned themselves up before leaving him tucked over the floor of stone they both vibrated into soft sand, still bloated and slowed down for the following years, maybe even decades before he was back at top shape.

Sighing as she got up, Twilight looked up at the ley lines Rainbow had to keep running by running inside them. With him sleeping and later slowed down, it would take for him to push his limits every moment of every day of the following century to prevent them from collapsing. And that was exactly what she wanted for him. To keep having limits to push through in this endless task she gave him. He would become mad otherwise, living a whole lifetime in the literal blink of a mortal's eye.

Twilight walked away from Rainbow, making the door materialize in front of her and leaving him to his imprisonment.

Author's Note

[Sigh] So, there's a heatwave going on where I live and it's made focusing harder. specially on smut, that already heats up the body. If you see too many mentions to heat, sweating and exhaustion, blame climate change.

On a more serious note, yeah, I tried to write more smut here, as well as amping up the darker undertones. All in line with how I picture Rainbow as a character; intense and dynamic, and a hard contrast to the more constant and calming Applejack.

Also, to avoid any confusions like last chapter, Rainbow here is gender fluid. Twilight just caught him in a 'male' moment, but he goes from woman to man to nonbinary at any rate. If you're curious, his names for each gender are Dash (woman), Blitz (man) and Flash. Not that he has too many people to communicate that when running forever to generate the magic of all the planet.

Finally, hope you enjoyed. It'll probably take another week at least for the next chapter, so I thank you all for your patience.

I wonder what to do with her, though.