Archive of Our Own

The night sky was lit by sparkling skyscrapers from above and police sirens from below, as the back and scarlet clad figure looked down from a nearby rooftop. The one and only Batwoman of Gotham was perched carefully on the precipice, her crimson locks draping over her shoulders and the white slits on her cowl focusing on the scene below her.

The military woman known half the time as Kate Kane was well into her night as Batwoman, patrolling the streets and following up on intel, when she had been pinged by Oracle that a possible Poison Ivy incident was occuring at a museum close to where she was. Knowing that Gotham’s main protector was out of town on Justice League business, Kate had taken it upon herself to help keep the city together while Batman was gone, whether or not she was asked to do so. Typically a loner, Batwoman accepted and gave crucial info to the extended Bat Family when needed, but times like this, where she could inspect a crime scene and take things at her pace were where she thrived.

Batwoman’s gaze was fixed on the entrance of the damaged museum, where tons of dense foliage blocked the police from entering the doorway. It was obvious that Ivy had done it, although robbing a museum was far from her normal modus operandi. While the cops at ground level were stymied by the thick forest, Batwoman was free to move above and cast her gaze to the roof of the building. The skylight had been torn open, she could see, along with a trail of decaying vines leading out of it, another sure sign of Ivy’s involvement.

She grimaced; the tabs she had been keeping on Pamela Isley, her girlfriend Harleen Qunzel and their strained associate Selina Kyle had let Batwoman know that their bodies had been changing recently, growing taller and thicker in more ways than one. It was hard to believe, but not much harder than Man-Bat or Clayface, so she took the cautious approach and waited for them to make a move. It was unfortunate that their move had occurred when her attention was elsewhere, but Batwoman wasn’t worried; the trio wasn’t hard to track.

Then, she saw it. A flash of darkness past the skylight, the barest hint of something moving along the rooftop. It was enough to make Batwoman act, and with fluid grace, she leapt from her perch and fired a grappling hook at the museum roof. The device quickly pulled her across the sky, her bright red hair and cape fluttering behind her, and in moments she landed on the opposite building. Another minor shift in the shadows beyond the light of the museum interior, and Batwoman could just make out several figures swiftly fleeing the scene.

They won’t get far. Batwoman thought, and dashed into the shadows herself. Moving past the machinery, air vents and railings surrounding the edges of the building, her cowl’s eye covers adjusted to night vision and gave her a much clearer picture of what was happening. There were multiple people scattering across the rooftop in different directions, each dressed in pure black with no features distinguishing one from another, and each of them had what looked like a satchel tied to their backs. She realized that she would never catch all of them, and settled on chasing down the closest one to her to interrogate them.

With intense focus, Batwoman sprung to the side, whirling around an air conditioner unit and getting a good sight at her quarry leaping midair towards a nearby building. Acting on well honed instinct, she pulled a bola out of her utility belt and flung it at the figure, the rope whirling around and ensnaring their legs. Balance lost, the figure could only tumble onto the opposite roof and collapse, while Batwoman was already leaping across the gap. Before the figure could untangle themself, Batwoman stomped one bright red heel onto the figure’s shoulder, pinning them on their stomach to the roof.

“You mind telling me what it is you’re doing up here?” Batwoman said in a tone that implied it was a demand, not a question.

“Mmph… I have no words for your kind!” The figure spoke in a high pitched voice, leading Batwoman to believe it was a woman. “Your filth will be cleansed from the Earth soon!”

“League of Assassins, then?” The assassin stopped struggling at Batwoman’s question, implying she guessed right. “What does Talia al Ghul want from Gotham this time?”

Before she could get an answer, Batwoman noticed the satchel on the assassin’s back was moving, almost like it was inflating with air. The assassin noticed too, and seemed to panic. “You fool! Your meddling is setting it off!”

“Setting what-” Before she could finish asking, the satchel suddenly burst open, releasing a wave of green vapors directly at Batwoman, coating her costume and spraying onto her exposed mouth. She couldn’t help but breathe in a large amount of spores that she surmised had been stored in the satchel for transport. Batwoman coughed and involuntarily eased her stance on top of the assassin, giving them the opportunity to shake her off and release herself from the bola. Before Batwoman could stop her, the assassin bolted from the rooftop, the exploded satchel still attached to her back.

“*koff* Damn it… *koff*” Batwoman coughed, struggling to breathe. What had likely happened was that the assassins had been collecting samples of Poison Ivy’s unnatural vegetation, though to what end she couldn’t figure.

Regardless, the surprise had allowed her only lead to escape, leaving Batwoman with little to show for her efforts but clusters of spores on her suit and in her lungs. That wouldn’t be enough to stop her investigation, though, as she already had plans to analyze the evidence so helpfully stuck to her body. As soon as her coughing fit died down and she composed herself, Batwoman leapt off the rooftop and made a beeline for her headquarters, surprised at how energized she was feeling…

—

“You’re home early.” Beth Kane remarked as Batwoman slinked in through the window. The blonde sister of Kate was relaxing on the couch reading a book as the black and red vigilante made sure the window was closed.

“Something came up.” Kate Kane carefully lifted the cowl off of her head, the bright red, long wig coming with it, revealing a much shorter haircut, trimmed short on the sides and left longer on top. Her brow was furrowed over her green eyes, and her bright red lips were pursed in concentration. “We’ve got some unwanted guests in the city, and I need to figure out what they’re up to.”

“So,” Beth closed her book and stood up, moving towards her twin sister. “I take it you’re going to be spending the rest of the night in the lab?”

“I’m going to have to.” Kate smiled grimly. “Poison Ivy is involved somehow too, and she’s too dangerous to ignore.”

Beth inspected Kate, worried. She wished she could help somehow, but Beth was nowhere near her sister in terms of detective skills, so she could only support her pale sibling with words and comfort. In addition to her concern over the stress Kate was under, Beth also noticed that the redhead was looking… different, somehow. Beth studied Kate for a moment before realizing that she looked taller than usual. The two were twins and had always remained the same height, but now it looked like Kate was slightly taller than Beth. New boots, perhaps?

“Something wrong?” Kate noticed Beth was staring at her.

“No, no, just… wondering how you’re feeling.” Beth asked.

“Honestly? Not bad.” Kate replied. “Lots of energy I haven’t been able to burn yet, is all. I’ll be fine.” She wasn’t lying; Kate did feel pretty good, though she wondered what was causing it. Adrenaline, probably.

“Well, in that case,” Beth was still worried, but knew that Kate could take care of herself. “If Batwoman is in for the night, maybe it’s time for Red Alice to hit the town?”

“...Are you sure you’re feeling up to it?” It was Kate’s turn to be worried, knowing that her sister’s mind was in a fragile place. But she also knew that it was good for Beth to get out, and feel like she was helping. If it took her other identity to do so, Kate could hardly say no.

“With Batman gone, Gotham can use all the help it can get, right?” Beth said.

“True.” Kate had to concede. “Just look out for assassins, alright? There are a handful of them on the streets, and I can't be sure where they’re headed.”

Beth nodded, understanding the risks. She couldn’t operate in Gotham without knowing what she was getting into, of course. Kate wished her well, and the two split up, Beth heading to her room to suit up and Kate heading to the hidden elevator that led down to her secret hideaway. Kate could swear she was feeling more constricted in her suit as the elevator descended, as if it were tighter than it should be. She didn’t want to say it to Beth, but she was worried the spores she inhaled were affecting her mind.

As soon as the elevator opened, Kate moved briskly through the computer lab she had set up on the floor underneath her large apartment. It wasn’t quite a massive cave under a mansion, but it was more than capable of what Kate needed. The dim, dark room that she kept hidden from view was filled with computers and spare equipment. On the way to the main, bat-shaped computer on the opposite side of the spacious room, Kate passed a large full length mirror she normally used for suiting up, and caught a glimpse of herself in it making her freeze in her tracks.

Even at a glance, Kate could see that she was taller than she had been earlier that night by at least a couple inches, her black Batsuit managing to stretch along her lengthened limbs and torso. Worse than that, though, was just how bulky she looked. Far from small and frail usually, Kate looked like she had been weightlifting like crazy, biceps and quadriceps bulging out, creating new curves on her limbs while her torso was thicker all over, her waist straining her utility belt and her chest looking hefty with pectoral meat.

“Damn, how could I miss this?” Kate asked herself, hearing her suit creak as she breathed. She needed to find out what was in the spores, and fast.

Hustling over to the computer, Kate immediately began typing and bringing up files to inspect. Information on Venom serum, the Monster Men, and any other mutative incidents that had occurred on Earth flooded the screen for her to inspect, but before she did, she needed more information on the spores themselves. Nearby was a medical station, from which Kate pulled a cotton swab and scraped it along the inside of her mouth, getting her DNA as well as spore residue on it, then taking it to the main computer. Opening a slot on the side, she placed the swab inside for the computer to scan and analyze.

Having done all that, Kate sat down at the chair in front of the computer, feeling her suit groan against her glutes as she did. She blushed; she was getting larger all over. Even her forearms were swelling, making her scarlet gloves bow outward, the same happening to her calves and boots down below. Taking a deep breath to calm down, her chest expanded more than it ever had before, distending the sharp, angular bat insignia, then when she released her breath, noticed that her chest didn’t shrink back down. Her pecs had grown that much bigger in just seconds.

Doing her best to put her concerns aside, Kate began to read up on the articles the computer displayed. She scanned the files as quickly as she could even as she could feel her muscles grow- it was slow, but her body was increasing all over, straining her suit. If she wasn’t in such a hurry, she might have taken the time to undress, but her suit was durable; Kate was confident it would hold out until she found a solution.

It took her very little time to read through all the information her computer had in store, leaving her with not much to go off of. She was growing slow and steady, she could tell, and none of what she was looking up matched that type of transformation, nor did it mesh with coming from Ivy’s spore pod. Raising a hand to her face to pinch the space between her eyes, Kate could feel her bicep begin to collide with her pec, the muscles rubbing against each other in a satisfying manner. A blush rose across her face; being bigger certainly felt good…

“Ugh, what am I thinking?” Kate protested to no one, standing up. It was not the time to focus on physical pleasure. Quickly, she inspected the DNA scanner to see that it was still processing, meaning she would still have to wait. Displeased, Kate took a short walk back to the mirror to get a look at herself.

She was certainly bigger, in more ways than one. Not only was she getting thicker with solid muscle mass, but she was still inching up in height as well. If she had to estimate, Kate would guess she was at least 6 foot 5 inches, half a foot taller than when she started growing. Not to be outshone, her muscles were still growing wider and denser, swelling deltoids making her shoulders more broad than any woman she ever met and more than most men’s. Kate’s abs were visible through the fabric of her costume, with obliques emerging out her sides and leading to growing lats, making her torso much thicker all around and putting harsh strain on her utility belt with her expanding waist.

Overall, Kate was feeling more and more like a brute than the lithe soldier she was used to. She still maintained her grace, though, enough for her to smoothly walk back to the computer and double down on her research. As she sat back in the chair, it noticeably groaned along with her overstretched outfit. Her weight was increasing dramatically with each inch of dense beef she was packing on. Getting more worried, Kate broadened her search to include various kinds of Kryptonite and radiation effects, and hoped the DNA test would be done soon…

—

Back on the streets of Gotham, Beth was patrolling the streets as Red Alice, and having a much less eventful night than her sister. Zipping through traffic at high speeds on her sleek motorcycle, she’d heard through her police scanner of yet another crime taking place in the city and was on her way to head it off. So far, Red Alice hadn’t seen much action- no assassins nor super villains to fight with, which she was sure her sister would be pleased to hear. It made for a boring night, though, so when she got news of a break-in and that it was near her location, she immediately was raring to go.

Ever since Batwoman had returned for the night, Beth had felt like she wanted to burn some energy. While she knew the job she was volunteering for was something to take seriously, she couldn’t help but look forward to getting out in the world and busting some criminal heads. So, she had suited up in her fancy dark red corset and tights and smeared black makeup across her eye line, the thoughts of action and fighting making her heart race as she went to their secret garage to await news of any illegal activity.

Beth had remained idling on her motorcycle listening to police reports for a good while, not noticing how her clothes were slowly growing tighter. By the time she raced out of the garage into the streets, Beth had to adjust her stance on her bike as her legs had grown subtly longer and thicker. The vibrations of the motor and adrenaline running through her veins was enough to mask it for the time being, though, and soon she was nearing the alleyway where the break-in was occurring. As she approached, Beth turned the motorcycle off and let the bike coast- or tried to, as when she stuck her legs out for support, her feet collided with pavement, causing her to lurch.

“What the…?” Beth muttered, trying to keep her voice down. Fully stopped, she stood up and finally noticed that she was several inches taller than she had been when she left the apartment. Never short before, she was now well over six feet and loomed over the motorcycle. She marveled as she ran a hand along her thigh, feeling and admiring its increased hardness and length. The garter belts holding her dark stockings up were stretched to their limit as the muscle underneath flexed, her tights pulling up her longer limbs.

Before she could examine herself further, however, a shrill voice cried out from the alleyway she had stopped just short of. Ignoring her problems for the moment, Beth bolted forward with a shocking amount of speed and lunged into the alleyway. Within, a couple of larger men in ski masks, likely just a pair of hoodlums, were accosting a much smaller young woman, one of the men holding her back and the other reaching into a broken window.

“Please! Stop! I don’t even have much!” The woman wailed, while the men chuckled.

“Dat’s okay, sweetheart, you got plenty for us!” The one holding her brought a hand up to the woman’s neck. Then, with a meaty thunk, a short throwing knife was embedded in the man’s hand. “AHHHHHH! What the hell?!” He screamed, releasing the girl.

“Huh? What’s-” The other man stopped rummaging through the window in time for a burgundy boot to kick him in the stomach. Completely out of breath, the shocked robber fell to the ground at Beth’s feet, the vigilante herself carrying several knives between her fingers, stepping over him and walking calmly to where the other man stood cursing with a knife in his hand.

“Gah, it’s one a’ you freaks!” With his uninjured hand, he reached into his coat for what could only be a pistol.

Faster than the man could react, and faster than she thought herself capable of, Beth launched herself forward, her thighs tensing and bulging large enough to snap the garter belts and show her pale white flesh. Before the man could pull his gun out, she delivered a swift kick to his side, hammering him against the brick wall and knocking him unconscious.

Beth relaxed as best she could as she determined that the danger was over, but her thighs remained taut and ripped, well defined quads having torn through the tops of her stockings, as large as full grown watermelons and giving her a harsh pear shaped figure. Adrenaline wearing off, Beth returned her remaining knives to their holsters and turned her attention to the woman she rescued.

“Th-thank you!” The woman said as she climbed to her feet. “Are you… from Themyscira? I heard about Amazons online…”

“What?” Beth replied, confused, until she realized that she was in fact towering over the small woman, over a foot taller than her. Then there were her muscles- now that her thighs had burst free, Beth noticed that the rest of her had grown thicker and denser as well, her outfit struggling to contain her. She was built as if she had been weightlifting all her life, bulging biceps, calves, pecs and more all bursting with strength. She felt powerful. “Listen, you should call the police before these men wake up. I have to go… take care of some things.”

The woman nodded and ran back into the building, leaving Beth alone. Seeing that she was by herself, the jacked vigilante turned her attention to her rock hard quads, her now standout feature. They were big, enough so that the bottom of her ruffled corset could barely drape over the top of them. Softly at first, Beth began to fun her hands up and down each thigh, finding a strange pleasure in how large she was, then she tried to press her fingers harder into her flesh only to be met with steel resistance, unable to dent her hefty muscles. Beth bit her lower lip; she was beginning to get turned on.

“Mmf… that’s enough.” She said as she reluctantly stopped feeling herself, realizing that she needed to tell her sister about this. As good as it felt, it wasn’t normal to suddenly grow like this. Walking back out of the alley to her even more ill fitting bike, Beth wondered if Kate would even be able to believe what had happened to her…

—

“Ugh, come on!” Kate shouted in frustration. The DNA scanner was almost done- it had to be, she had been waiting for it for hours. She had exhausted all of her research possibilities, finding nothing in her vast library of information that could explain her growth, so getting actual raw data from the spores and her own DNA was her only shot at figuring out why she had become so massive.

Kate’s Batsuit was barely hanging on, every inch of the hi-tech super durable fabric stretched to the limit to cover her gigantic bulging muscles. Her growth had never slowed down all night, and hundreds of pounds of feminine beef had piled onto her frame. Pectorals as large as medicine balls jutted out off her chest, enormous slabs of rippling musculature, pushing up so tall that Kate had no choice but to rest her chin in her hard cleavage. Her traps had grown so mountainous and thick, inching up above her head, that her neck had all but disappeared, leaving her head to look as if it was plopped right on top of a muscular caricature of a woman.

Biceps almost as big as Kate’s pecs struggled to push inwards, colliding with the rest of her meaty torso as she tried to keep her hands in front of her. Kate’s deltoids were an immense shelf on either side of her, over eight feet wide at their peak; she had still grown somewhat taller over the night but not nearly as fast as she had grown thicker, and her shoulder width was actually wider than she was tall. Lower down on her body, Kate’s abs had multiplied and swollen so large that they jutted out of her stomach like a tremendous gut of pure muscle, with gigantic muscles wings bowing out from her underarms mashing up against her dozens of cobblestone obliques. The red cape that she used so dramatically in the field now only just covered the top third of her beastly back, her body so huge on all sides that she was more of a wall of sheer muscle than a human figure.

Below her gigantic waist, Kate’s quads had exploded into more deeply defined, overgrown brawn with huge calves bulging beneath, however the real growth was happening just below her strained utility belt- a large, suspicious bulge had been swelling in the crotch of her costume, the dark black material keeping it tucked away for the moment. Kate could feel it throb, and had an inkling as to what was going on down there, but unable to see or even reach down that far anymore to check, she was stuck waiting for either her growth to end or her clothes to finally fail to hold her mass back.

Then, with a ping, the Batcomputer displayed the words “ANALYSIS COMPLETE.”, ending Kate’s long wait. “Finally!” She said, frustrated. Hopefully whatever the DNA scan had to tell her would be helpful.

“ABNORMALITIES DETECTED:” The screen displayed. “PROJECTED OUTCOME ON HUMAN BODY: MUSCLE TISSUE DEVELOPMENT ACCELERATED BY 1000%”

“I- mmmph- already know that!” Kate groaned and blushed as her body surged. She could feel every muscle fiber from the neck down strain and swell, the feeling being much more sexually pleasing than when she had first begun her growth.

“BONE DENSITY INCREASED BY 802%...”

“Uhnnnnnffff…” Kate’s patience was wearing thin, and she had to resist the urge to slam the desk in frustration, sure that she would demolish it with her massive meaty muscles. Her Batsuit, built to withstand immense amounts of stress, was itself wearing thin as well, the micro seams holding the military grade fabric together pushed to the breaking point. She desperately wanted to maintain her modesty, but her body wasn’t agreeing with her.

With a loud pop akin to a gunshot, Kate’s immense pectorals tore through the red Bat logo on her chestpiece, revealing her pale white flesh, deep striations of muscle sinew bulging up and out, practically burying Kate’s face in her own chest. Her nipples were pert and pointed, as rock hard as the rest of her body. Only seconds later, more of her suit began to burst off of her, sleeves splitting down the length of her overgrown beach ball-sized biceps, ripping all the way up to her broad and heavy deltoids, over a meter of meat on each side of her growing exposed to the bright computer lights. Kate’s traps were next to be freed, a veritable mountain of muscle towering about her and threatening work together with her pecs to swallow her head.

“SKIN HARDNESS INCREASED BY 1068%...”

Thankful that she at least wouldn’t burst out of her own skin, Kate kept billowing out of her clothes, the material formerly pressed tight against her gut of hefty abs peeling off as a sea of obliques tore the sides of her suit to shreds. Quads as large as her biceps emerged from their confines in all their muscular glory, her taut and sizable glutes freed from behind her, while both her forearms and calves split her red gloves and boots down to her hands and feet.

“LIKELY SPONTANEOUS GENERATION OF HYPERTROPHIED MALE GENITALIA…”

Barely able to read the last sentence, Kate’s suspicions were confirmed- a thick, weighty penis sprung out of her loins, destroying the last of her costume and her modesty. Besides the remains of her gloves and boots, Kate was totally nude, a gigantic muscle meatball with a girthy cock and two basketball sized testicles, churning with virile seed.

“D-dammit… Can’t… focus…” Kate groaned. Her libido had been spiking for a while, and it was finally becoming more than she could take. The several foot long, ultra thick cock bumping against her muscle gut was demanding too much of her attention.

“POINT OF ORIGIN: INDETERMINATE. FURTHER STUDY ADVISED.” The computer finished displaying, leaving Kate with no real leads. Not that she was concerned at that point, she was too focused on her own throbbing body to think about why it had grown so massive.

“Need… release…!” Kate stumbled backwards from the computer, the floor warping beneath her weight; if she hadn’t been in her reinforced secret lab, she would likely have broken through the floor hours ago. Her giant dick was ready to explode, veins throbbing on the sides as her balls rumbled and groaned. Kate needed to ejaculate, badly.

Unfortunately, her attempts at jerking herself off were less than fruitful- Kate’s giant arms could barely bend forward, her enormous biceps bumping into her equally gigantic pecs. Even stepping backwards like before was a chore, her legs too muscular to properly bend. Kate was too huge, too cumbersome to move like she was used to, instead only able to flex her mighty muscles in an effort to generate enough friction to get herself off.

So engrossed in her labors, Kate didn’t even notice the sounds of the elevator behind her descending from the floor above. In a few moments, the elevator door opened and revealed an amazonian Beth Kane.

“Kate, something weird is going on!” Beth started as she entered the lab, needing to duck down to fit under the threshold. “Somehow, I started… to…” Beth trailed off as she registered what she saw: the behemoth back muscles of the giant meatball that was her twin sister. “... grow.”

“Ah! Beth!” Kate snapped to attention, feeling both relieved that someone was there and worried about what Beth had said. “This happened… hng… to you too?!” She instinctively tried to look over her shoulder, but felt her cheek collide with steel hard muscle.

“Yes, but…” Beth didn’t know what to say. Her own growth had continued through the night as well, inching taller and wider until she tore through most of her clothes. Peaking at 9 feet, it had gotten to the point where she couldn’t even ride her motorcycle anymore and she was forced to carry it over her shoulder on the way home. An easy task, seeing as she had bulked up significantly, large, powerful arms having burst from their sleeves and chest expanding until only her red corset remained intact. Further down, her legs were also naked barring the bottom of her boots, with gargantuan thighs jutting out off her frame, immense and shredded, powerful enough to allow her to kick through solid lead if she so desired.

And yet, despite her impressive transformation, Beth could not even compare to Kate’s sheer size. Beth was huge, while Kate was colossal, bulging, rippling muscles piled all over her, stretching wide and tall to degrees Beth could only imagine. She was very concerned, but even more than that, she felt… jealous? Subconsciously, she began to stroke her own giant quads and imagined herself that big, that overgrown with muscle- what must that feel like?

“Beth?” Kate called out. “I really need your help!”

“O-of course!” Beth snapped to attention. “Just tell me what you need me to do.”

“Okay, I need- hrgh- I need you to not freak out…” Kate was struggling to concentrate, her libido as strong as her mighty physique. “Come around to the computer…!” Beth did so, stomping on the floor with her own weight, looking Kate over as she moved, studying her muscles, her absolute girth and size, and her…

“What the hell is that?!” Beth shouted as she saw Kate’s erect monster cock.

“Beth! Focus!” Kate demanded, trying to do the same. “Go to the computer and I’ll walk you through the steps.”

“O-okay…” Beth was close to freaking out- Kate’s new organ was far more than what Beth herself had experienced. Still, she did as she was told and went to the computer, placing her fingers on the keyboard. “What exactly are we planning on doing?”

Kate’s face was flushed, thoughts of orgasming still pervading her mind. She knew she would need someone to help figure out why she had grown, but also to help her finally get off. “Calling for backup.”