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Chapter Text

Zeroth Law of Thermodynamics: if two thermodynamic systems are both in thermal equilibrium with a third system …

Ship Five hummed smoothly under Rem’s feet as she walked through the bay, routine inspections of Plant, human, and cargo ships having been done and path adjustments having been made. It was on her shift months, when the rest of the crew and passengers were under cryosleep, that she had the most time to think. Of course, under cryosleep, only the bare minimum of brain activity was allowed, so dreams eluded her. But even when she was awake during non-shift months, she was so wrapped up in making up for lost time that she didn’t get the time to plan or think or… do anything beyond celebrate another milestone or give another poor engineer some company.

Of course, the time to think, as craved as it was, also brought back waves of guilt and memories of trials. Not just metaphorical trials, either— no, the memories of Tesla’s haunted eyes and her trembling body flooded her mind. Rem was, without a doubt, complicit in the suffering of a child, and despite the soothing murmur of machinery and the hum of the engine, she could not–hell, would not–shake the memories of Tesla’s desecration. It was after the pieces of her had been stuffed into small Plant vessels, after the experimentation ended and her suffering began anew, that Rem finally laid hands on the Bible again.

It used to be a thing of comfort, back on Earth. She had never been particularly religious, but the book was a comforting weight and there were morsels of good advice in those dust-lined pages. And so, after Tesla had been cut up and discarded like a piece of meat, Rem stormed back to her room, flipped open the Bible, and prayed .

She doesn’t quite remember what she prayed for now, other than simply begging for a chance to do better, be better, fix her mistakes, atone for her compliance. And maybe, maybe, to redo the rearing of a child once more, just for a chance to make Tesla proud.

She’d always told Rem that she wouldn’t mind a younger sibling.

Said chance–no, chances –to do better started calling for her, twin voices harmonizing with the ever-present hum of the ship, and of the Plants. She chuckled lightly, making her way to the common area at the heart of the ship.

“Rem!” Vash wailed, crocodile tears leaving glistening tracks on his face, pointing at Nai accusingly. “Nai stole my comic books! The ones about the ranch and the cowboys!”

Nai whipped around to stare wide-eyed at Vash, affronted, his bangs falling over his eyes. Rem really needed to find someone else to give him a haircut, regardless of how cute he looked. It was clear the twins abhorred the haircuts, even if Vash was too polite to say so, and Nai would get pinched by his brother if he got too mean.

“Stole— I didn’t steal them! I borrowed them, and I was gonna give them back!” He huffed. “Besides, I like cowboys more than you do.”

“So?! Those are mine!” Vash turned to her, pouting and crossing his arms. With his ruddy cheeks and glistening blue eyes, he almost looked like an angel. A bratty one, but an angel nonetheless. “Rem, make him give them back.”

“Well, I was gonna give them back today, but now I won’t,” Nai snapped. It almost scared her how sharp and adult he could sound when angry, even if his words were anything but.

Rem sighed fondly, shaking her head. “Boys, if you don’t stop fighting and blaming each other, I’m going to confiscate all the comics.”

As expected, that quieted them down quickly. Vash brought his hands in front of him, wringing them and shuffling on his feet, a new swell of tears already lining his eyes. Nai stood stock-still, gaze fixated on the floor even as a tint of pink rose to his fair cheeks. She took a moment to marvel at their synchronicity, at how they balanced each other in something as base as shame : the sputtering spitfire and the steaming drizzle.

“Now then,” she said, crouching down to their level. How time had flown— they were just a few months from their first birthdays! “From the top: what happened?”

Nai cleared his throat, voice scratchy as he mumbled, “I took Vash’s comic books.”

“Stole—!”

“Vash,” Rem warned, giving him a stern look. He deflated. “Nai, did you take them without permission?”

He nodded mutely, the pink flush rising higher. She pursed her lips, turning to Vash.

“And how did you react?”

His eyes widened, and she could see the cogs turning in his head. For all his naivete and innocence, the kid was knife-sharp when he wanted to be. Unfortunately for him, Rem had two decades on him. She raised a brow.

“Don’t you try to lie, mister.”

He jutted out his lower lip, employing his signature pout-and-puppy-eyes. Typically, Rem would melt at the look, but his twin was seething quietly next to him, and someone had to maintain the balance. She just doubled down on her stern glare, and, finally, he relented.

“I— I called him mean and s-stupid,” he mumbled thickly, before the tears spilled over and he launched himself at his brother. “I’m sorry, N-Nai! I didn’t mean it! I was just— was just mad!”

Nai steadied himself, grunting slightly as Vash slammed into him. As if on instinct, he wrapped his arms around his brother, pulling him impossibly closer. If Rem wasn’t busy making sure they didn’t turn into an argument again, she would have cooed and pulled out her personal camera, much to Vash’s embarrassment and Nai’s chagrin.

“I forgive you,” he whispered into Vash’s golden-blond hair. Hesitantly, he glanced at Rem, a question and a plea written in his bright eyes, even as his mouth turned down into an impassive frown.

She smiled warmly, nodding. Something in his posture, as minute as it was, relaxed, and he buried his face in Vash’s shoulder.

“...I’ll ask next time,” he said, voice muffled. Vash laughed, the sound bell-like and clear, exchanging an amused glance with Rem. They both knew very well that it was the best apology he was getting.

“Okay, Nai,” he said brightly, “Thank you.”

And then, with little warning, Vash jumped into Rem’s arms, dragging Nai behind him. She laughed brightly, squeezing them as close as humanly possible. Vash wriggled in her grip, pleased, and Nai relaxed incrementally, until she was supporting all of his weight. Settling onto the ground, she pulled them more comfortably on top of her, dropping a kiss onto each of their foreheads.

“Thanks, Rem!” Vash chirped between his giggles. “You always make us feel better.”

“And you stop our fights,” Nai added quietly, “It makes it easier for us.”

She smiled, bigger and brighter than she had in the entirety of her shift today. “Anything for my perfect little boys. Bring it in!”

…then the two systems are in thermal equilibrium with each other.

Chapter Text

First Law of Thermodynamics: Energy cannot be created…

Vash’s bones felt heavy, lead-like. He could track the rot as it coursed through his body, settling at the base of his skull. Come morning, his hair would be a smidge darker, his eyes a touch duller. A fair price to pay for easing the burden of one of his sisters.

— — —

Contrary to popular belief, rot was sweet. It flowed like honey through his veins, warming him inside out. It was right near addictive, too, with the head rush that followed the overexertion of healing or… manifesting. Vash knew what overextending himself implied, his heart beating louder and harder each time–hell, his resting heart rate was around thirty percent higher than it should have been at his age–, but it felt nice. It felt good.

He could do something, anything to help. It wasn’t like Vash was the perfect Plant anyway, so it was only correct that the rot took hold easier for him than for his siblings. He couldn’t generate anything useful, he could only take and maim and destroy— it brought him back to the first time Rem showed him and Nai flora. He’d said that all he was good for was eating and sleeping, and every passing day proved him correct. Every passing moment proved him correct.

He supposed all their creation had to be countered with sheer destruction. That was another tenet that Vash the Stampede had proved false by fault of his being: creation.

He knew that Plants had a finite source of energy. He knew it in the way he knew he had to atone, he knew it in the way he knew when his brother took time to rest after either one of them overtaxed themselves. He knew it in the way he knew he could never rest, not until every vestige of energy had been used and this was over.

There was another misconception, this one far more dangerous than a misreading of rot’s characteristics: Plants were perfect nuclear generators. They–his sisters, that is, because even Nai has a limited arsenal in these regards–were not. They were close, of course, and the efficiency of their energy processes was yet unmatched, but it still took a toll on them. Pushed them closer to disorder.

Vash couldn’t exactly fault the humans for this idea; after all, Plant energy loss was near immeasurable for them without Lost Technology. But it was insidious, subtle in the way it slipped through the Gate and into their bodies. It would not be found until it was too late and his sisters had gone red, preparing for a Last Run.

It began like this: fever.

Plants, including himself and his brother, ran cold despite the processes they undertook. Any heat produced during creation dissipated easily, taking with it minute amounts of their finite energy. But–and this was where he stood now, fighting off a dangerous flush–if they drew upon too much power in too little time, that heat could not dissipate, and the rot had an even wider chasm to flourish in. This was the first time humans could measure their thermal outputs, and it was the first time they would fail to realize what it meant.

Soon enough, as the demands came incessantly and there was less and less time to recuperate, the heat simply could not dissipate fast enough. Energy turned stagnant, and stagnancy breeds miasma. This was when the whitish-blue of a healthy tank turned into a beautifully foreboding violet, deep and true and concerning.

It was the state Vash found his sister in in this nameless town. Somehow, despite its miniscule population and low energy demands, they were still overworking her, drawing out everything they could. Her low, pained moans reverberated in his head as soon as he was in range to connect with her, and the familiar brush of connection was enough to set his heart racing. He was tired, but she was exhausted. He had sighed quietly, sending back as much comfort as he could and promising to visit before leaving, before withdrawing from the connection and willing his heart to slow down.

Sometime between a cheap bar dinner and seeing the others off for bed, Vash had slipped away with a quiet murmur. The streets were blissfully empty, and the generator housing the Plant was minimally guarded. It was easy to slip under the nose of the sleepy patrollers and even easier to find his sister, her moans having turned to wails over the course of a few hours. The Plant room was hot . He sucked in a harsh breath, sweat trickling down his neck and eyes roving over the reddish purple of her tank.

Sister? he asked hesitantly, prodding his way into her consciousness. She held little resistance, and her bulb unfurled, feather-like petals falling away to show her too-frail body.

HurtsHurtsHurts! TiredSickWeak! Can’tGive WantMoreMoreMore WeakPainHurts!

He planted his feet firmly on the rickety steel platform, letting the wave of distress and emotion wash over him, parsing through it what he could. She was tired and weak; he could help with that. She was in pain; he could reduce some of that. After another few moments, when the floodgates closed, he nodded definitively, striding forward even as his knees buckled.

Help , he told her gently, putting behind as much intention as he could. Here. Come here. Trust me.

TrustTrustTrust GratefulTiredThankYou Take?

Take , he confirmed, pressing his forehead against the cool glass of the tank, his sister mirroring him instinctively. Okay? Connected?

ConnectedConnectedContentGrateful TiredSickBetter? CertainlyBetter?

His huffed out laughter fogged up the glass between them as he pulled at his own reservoir of power, building a temporary pipe between him and his sister. It was then he realized just how low she was running; a few more days, and she would have gone red.

Definitely better , he responded shakily, closing his eyes and cutting off the flow of his emotions to his sister. She didn’t need to know the strain, not after all of this. I’ll give, you take.

A wave of grateful agreement, and he let the floodgates open.

She was younger than him, he realized, as she tentatively reached into his reservoir. She wasn’t quite as adept at controlling her output, allowing the town to take more easily than they normally would and having trouble replenishing her own stores. No one even realized it. Vash leaned more heavily against the glass, reaching into his energy himself and allowing an efficient trickle to pass through. She pulled at it desperately, a little faster than he would normally allow, but— she needed it.

As she pulled, he could feel warm rot replacing the lost energy, winding lazily around his body and through his veins. He blocked off those feelings too, not wanting to scare her off. Slowly but surely, he saw the shift in hue even from behind his eyelids. Reddish-purple turned to dark blue, which morphed into the pale blue-white of a healthy Plant. Gently, he severed the pipe, ushering the excess still trickling between them towards his sister. Instead, she pushed it back. He frowned.

Take.

A wave of denial. HappyHealthyContentThankYou Brother TakeBackNeed TiredShakingNeed

I don’t need it , he insisted. You’re young, you should take extra.

BrotherBrotherBrother TakeTakeTake! she insisted right back. If she could have crossed her arms, Vash had no doubt she would have. BackTakeBack YouNeedTiredSleepRestEnergy LimitedUsedFiniteLost LiveLiveLive

Oh, she was stubborn. He sighed, conceding this battle to her, and letting his energy slowly trickle back into him, displacing some of the rot. As he withdrew from the connection, he admitted, where she couldn’t hear, that she was right. He was tired— exhausted, really. Heaving himself off of the tank, he shot his sister one last smile as she wrapped herself in her petals once more.

Getting back to the inn, he had all but collapsed onto his bed, ignoring Wolfwood’s muttered curses from across the room. Healing his sisters drained him, but no one else could do it. They deserved that much, at least. Besides, he was hard to kill; a little infestation, a little rot, a little lack of energy, would do nothing to him. Nothing important, at least. 

— — —

That brought him to the morning, bone deep exhaustion still heavy on him, but they had to eat breakfast and leave. His glasses hid the worst of his dark circles and eyebags, enough so that Meryl and Roberto barely blinked an eye when he plopped down into a chair between them. But Wolfwood–goddamn Wolfwood –narrowed his eyes at him, slowly chewing on his cigarette. Vash didn’t miss the way his eyes paused at the roots of his hair, or how his gaze lingered on Vash’s eyes a little longer than necessary. He tilted his head, allowing the glare to hide away his eyes.

“Ya look like hell, blondie,” Wolfwood finally said, low enough that only Roberto raised a brow. “The fuck did ya do last night?”

He tittered nervously, shrugging. “I just decided to stay out a bit late! No harm in that, right?”

Wolfwood frowned. “Sure, whatever ya say.”

Vash shot Wolfwood a smile, one that didn’t land right based on the way his eyes darkened. He sighed. The rot settled at the base of his skull.

…or destroyed.

Chapter Text

Second Law of Thermodynamics: Disorder in the universe increases…

Wolfwood was damn certain that this was not how the fight was supposed to go. He knew Vash and Knives were powerful, extremely so, but this was on a whole other level of Plant fuckery. Vash had an iron grip on a swirling, pulsating purple cube as he expertly dodged Knives’s steel tendrils, parrying and shooting in equal measures as if he couldn’t feel the countless nicks from the blades.

Maybe he couldn’t. There were those Plant markings again, winding over his temples and cheekbones and chin, labyrinthine. Wolfwood knew they were in his eyes, too, so impossibly blue and bright and sparkling. He shook himself, jumping off one of the rooftops, running to where Meryl was. She was caught between a fight between the two brothers that would make or break this whole pathetic civilization. He almost felt bad for her; she didn’t deserve to get wrapped up in this dirty business. She should have been in the city, making good money and living a cushy life.

He couldn’t ruminate on that for too long, though. Another blast from Vash’s gun–poor thing had seen better days–, and he was launched back into the present. The present being: his feet pounding on rooftops, civilians and military alike yelling from the streets, someone who didn’t deserve to be wrapped up in all of this being wrapped up in all of this, and two brothers that would end the world. 

Risking a glance downward, he took note of where he could make a safe landing with Meryl— and of the destruction that befell JuLai. There were craters in the roads, collapsed street stalls, and shattered windows and crumbling walls. It was like a storm, a stampede , had run through this place. He made another jump, heart leaping into his throat as Meryl was knocked back from a particularly powerful blow between the twins, her footing slipping. She was seconds from plummeting to her untimely death, and he was seconds from witnessing it.

For all that was utterly, irrefutably good about Vash, one thing remained true: destruction and disorder followed him everywhere he went. It didn’t matter if it wielded a cross or a million knives.

Wolfwood made it just in time, grabbing Meryl’s wrist right as she began her descent. He could feel her tense under his fingers, her bones straining against his grip, but he didn’t have time to worry about that right now. He could feel Vash’s gaze, ever careful, burning into his back as he hauled Meryl up. With a split-second glance at the brothers, he made a break for it.

He swore he saw Vash smile one of those rare, beautifully true smiles.

— — —

Meryl’s shoulder was heavily bruised and only a few wrong movements from a full dislocation. Even still, her eyes were fixed on JuLai’s spire, towering and shimmering gold in the city lights. For the first time, Wolfwood really considered the order and harmony that went into building something like JuLai and its spire. Everything was well-organized and well-balanced, locked in an eternal dance of give and take, stress and destress. Any deviation from its preordained order, and everything would collapse. But JuLai was sturdy, and civilization, loathe as he was to admit it, was sturdier.

Knives and Vash— Vash and Knives, Angels of gun smoke and bloodstains on No Man’s Land, threatened to throw all of that into the upset. For all of her stability and order, JuLai fell to her knees in front of them. At this distance, Meryl and Wolfwood skirted the outskirts. The two brothers were just pinpricks of light, pale blue and stunning violet, dancing through the streets and up and down the spire, dizzying in their rhythm. It was a morbidly beautiful routine, and Wolfwood was compelled to watch, having played a hand in its choreography. A regretful, horrible hand in death once more: the death of Vash the Stampede, or the death of civilization.

Meryl sucked in a harsh breath, knuckles going white as she clutched at her shoulder. “Wolfwood.”

He hummed.

“Do you remember what Vash explained to us about Plant colors? The ones in between blue and red?” she asked, her voice sounding small in a way that it never did. Never should have.

He cocked his head, face pulling into the same unimpressed raise of his brow and press of his lips as it always did. “Cut to the chase, Li’l Lady. I’m not in the mood to play games.”

She huffed, and the sound was so Meryl that he almost felt like things would be okay. Almost. “He said the shade of purple or blue indicated how much energy–how much life they have left–, and Vash’s color…”

He stiffened, watching the dance with a new fervor. Sure enough, Vash glowed a brilliant royal purple, teetering right on the edge of blue and red. Any wrong move, or any right move, could send him plummeting on either side. Wolfwood bit down on his cigarette, the bitter tang of nicotine and worm legs disconcerting in a way he had forgotten.

“Fuck,” he spat, spitting out the cigarette with it. He crushed it under his heel. “God fucking dammit, blondie!”

Meryl nodded blankly. “God fucking dammit, Vash.”

And if Wolfwood didn’t have the tears beaten out of him, that would have done him in. Even as it stood, his chest burned, tight, and he ached, the pain marrow deep. Because this was Vash approaching a tipping point, this was Vash being thrown into disorder, this was Vash having to make spontaneous decisions.

And all he had done was make it even harder.

JuLai, for all her grandeur and order, was going to fall by his hand, no matter how indirect. One of the Angels, too, was going to fall; selfishly, Wolfwood hoped that it was Knives’s end. Even death would be too kind for him, humbled by Vash. Kind, generous, pained, brave, cowardly, naive, world-wizened, angelic Vash .

Death would be too kind a fate for the crossbearer and the knife-wielder.

It was only fair that as the pale blue and brilliant purple fled to the skies, that Wolfwood was made to watch.

The world fell to disorder.

…for spontaneous processes.

Chapter Text

Third Law of Thermodynamics: A perfect crystal at zero Kelvin…

Meryl Stryfe was not meant to be helpless, but here she stood, twice in the same day, utterly useless.

It was one thing when it was Roberto–God, he was looking forward to his retirement. Why did it have to be taken from him?–bleeding out in the elevator, one hand wrapped firmly around the nail in his gut, the other fiddling with his flask. Meryl could have helped him, and she very nearly did, hands hovering anxiously over his, but he… refused. She doesn’t know why. It wasn’t like he loved life, but to just accept death like that— it felt antithetical.

Maybe the acceptance made it easier, she mused as she rode the elevator back up the spire, loading the derringer. If you had taken to finding comfort in death, then grief for yourself did not carry over. She wished it was that easy for the living left behind.

The elevator dinged as it reached the top, and with one last look at Roberto’s cooling body and the smear of blood on the wall and the pool of crimson around him, Meryl made a promise to the world: she would grasp her power, and she would use it .

That was how she had run into the central Plant room, the glowing tank making up the entire posterior wall— overzealous and angry. But, like a cold splash of water, reality washed over her. Because, as angry as Meryl was, as much as she wanted to tear Knives apart for what he had done, she was still only human . And this was a fight between these two brothers: it was anything but human.

Vash and Knives, typhoon and cyclone, moved fluidly through the tank’s fluid, parrying and attacking in equal measure. That damn old scientist just stood there, calling out percentages. Meryl had half a mind to shoot him in the back of his bald fucking head, but just then, Vash stilled.

Despite the scientist’s protests, Meryl screamed, running up to the glass of the tank, watching helplessly as he twitched with the steel tendrils embedded in his body, digging deeper and deeper . And— and every part of him crawled with the same dark rot, festering and teeming. As the percentages crawled higher, so did the rot. He was deathly pale and unmoving, and, for the first time, Meryl could properly see the exhaustion that laid deep in his bones. It fell like veil over him, not quite resignation, but certainly something that unsettled her to the core. Acquiescence, maybe. Sacrifice.

“Ninety-nine percent.”

And the world stood still.

Vines and wooden tendrils snaked out from Vash as Knives did whatever the hell he was doing to her friend, reaching out and towards their sisters, towards Meryl, towards JuLai. She stumbled back as the scientist spoke, laying out every gruesome detail of Knives’s plan for the end of humanity. And sure, Meryl was worried for humans, but at that moment, her mind honed in on one strange thing: Meryl Stryfe was supposed to clear Vash the Stampede’s name. She hadn’t even succeeded in that , and it was her entire job. It was what got Roberto killed.

It was a silly thing to think about, really, considering the brutality of the scene in front of her: at this point, Vash was being used more as a conduit, his sisters more as vessels. A sinking feeling in her gut told her that, at this point, Vash the Stampede was irrelevant. This was Vash the conduit, Vash the Gate, and there was little she could do to help him.

She would be damned if she didn’t try, though. It was the least she could do.

“The final step in the creation of his new world is to eradicate mankind,” the scientist said, reverence dripping from every word. Her stomach twisted, and she stepped forward.

“So you’re saying that if his plan works out, then we’ll all die?” she breathed, voice breaking. “Come on, Vash! Wake up already!”

“There’s no point. That’s not who you knew,” the scientist cut in, and he almost sounded sorry. “Vash the Stampede is no more.”

She fired the two shots Roberto’s– her –little derringer carried, helplessly watching as they bounced off the glass.

“Accept it.”

She was, in all reality, a contrarian. Vash the Stampede may have been gone, but that just meant she would have to crawl into hell to bring him back. And she knew, somewhere deep down, that he was tenacious. Whatever messed up sense of guilt forced him to eat lead instead of food would anchor him down with them, and she would be damned if she didn’t follow the line that was cast.

Meryl Stryfe was not meant to be helpless, and not even Vash’s deathly stillness would stop her.

…has zero entropy.