.

ENTROPY

Note: This story is not mine. It is written by talkingsoup over on AO3, and I am crossposting their story here with their permission to be able to share their wonderful work with the FFN community as well. A link to their account can be found on my profile.

Chapter 1: A Jump to the Left

Don't you know how to greet a new pal?

Sans hit the back of the machine and slumped to the floor, dazed. The hatch slammed shut; Sans reached for it, but too slow. There was a clank as the wheel spun and the hatch sealed with a hiss. All at once, the sounds—rending metal, the groan of the Core, distant screaming—died completely. Sans was left with nothing but his own haggard breathing.

He struggled to his feet, trying to reach the handle on the door, but with a high-pitched whine and a burst of light, the machine came online.

"No, no."

The hatch couldn't be opened while the machine was active. A failsafe that Sans himself had designed and Dr. Betas had improved on. Sans wished he could go back and punch himself in the teeth.

"D-Dammit…"

He took hold of the handle, but then the machine pitched violently to the side. Sans tumbled into the wall of the machine, somehow managing to keep his grip on the handle. The machine tilted further, and through the window, Sans watched as the catwalk finally gave way.

Everything fell, down toward the darkness. The machine rolled.

Sans caught one last glimpse of Gaster. Long enough to see the look of sorrow in his friend's eyes. Sans slammed his fist against the window and a sound tore from his throat, half scream, half sob.

In the last moment, Gaster summoned a few of his bullets and spelled out two words:

GOODBYE, SANS.

"No…"

The whole world went dark.

In the next instant, a roar filled the machine. Sans clung to the door handle, panicking. Out the window was nothing but black, but the interior of the time machine had started to glow. Particles of white light gathered around him and sparks leapt from the walls to his bones, stinging and burning.

"Oh god, oh no, no no no nonono—"

The machine activated, the void splintered, and pain hit Sans like a bolt of electricity. The light engulfed him. He felt himself pulled in all possible directions, but he couldn't move, couldn't even scream.

Was the universe being torn apart, or just Sans?

There was a sensation like unraveling, like tearing, and Sans blacked out.

Sans came awake on the floor of the machine. He was curled up on his side and wedged into one of the corners. Everything was quiet. Sans blinked slowly, trying to make the world come back into focus. He gave his fingers an experimental flex.

Every last bone in his body ached, but he was alive and whole.

He shifted, gritting his teeth against the pain and trying to push himself to a sitting position. He got about halfway there and ended up just slumping against the wall. The light was gone. It felt like the machine was resting on something solid. Sans peered up at the window. It was dark, but not void dark. He could see what he thought was a tree and the edge of a building roof.

Sans lifted a hand to his eyesockets, trying to massage the ache out of his skull. He needed to get up. Needed to figure out where he was and what had happened. Something was wrong. Missing. It felt as though his mind was full of holes.

He had been in the Core, in a room at the very bottom. The time machine above and pitch darkness below. There had been a fight. Then the doctor had thrown him into the machine and turned it on.

The doctor…

What was his name?

Sans pulled his hand away and stared at his palm. Panic began to well up behind his sternum.

"Doc…"

Why couldn't Sans remember his name?

They had all fallen. Sans in the time machine, the monsters who had followed them. And the doctor. All of them had fallen into the void, and…

Sans dragged himself upright, groaning, breath quickening. If Sans was alive, that meant the machine had worked. It had triggered a Reset. Sans looked out the window again. There was still a world out there. This had to be a Reset, and yet…

His head was pounding. Sans squeezed his eyesockets shut and pressed his hands to his temples. He couldn't think. There was a blank space in his memory, as if something had been cut out.

The doctor. His name. What had been his name?

"Okay, stay calm, stay calm…"

He stumbled to the door and caught the handle. It was more difficult than it should have been. The handle seemed to be skittering left and right, as if Sans was shaking violently. He pushed the door open and stepped out. His feet struck solid earth and Sans pitched forward onto his hands and knees.

Dirt, grass, air. Sans looked around. It was hard to focus on anything with everything vibrating so fast, but he recognized this place. Knew it like the back of his hand.

This was…his home. This was the tiny courtyard behind his and Papyrus's apartment.

Papyrus.

The panic inside him bloomed. His brother, he had to make sure his brother was okay, had to make sure he still existed…

He tried to stand, but everything was shaking. Vibrating. This wasn't an earthquake. He looked down at his hands. He could feel the earth beneath his fingers, still, solid. But his hands were shaking so fast they had become blurs.

"Papyru—"

Everything seemed to slip sideways. Terror drew a small cry from his mouth. Sans felt himself move without moving. He passed through something dark, then—

The world snapped back into place, only now it was snow beneath Sans's hands.

Sans gasped in surprise and tried to drag himself backward, only to fall into a snow drift. There was snow everywhere. He looked around, trying desperately to get his bearings, trying to understand where he was.

There was a forest in one direction, the stunted evergreens that had subsisted beneath the earth. He was still in the Underground at least. In the other direction were the lights of a town. He squinted. He recognized those buildings. He could even faintly see the neon sign over Grillby's.

This was near Snowdin.

He had traveled from New Home to Snowdin in the blink of an eye.

"Holy shit."

How? This made no sense. Sans hugged his arms, shivering mostly from panic. Skeletons didn't feel cold exactly, but that didn't mean the sensation was very pleasant. He was dressed for Hotland, not the snow.

He got to his feet, bones creaking.

"Okay." He scrubbed at his face. "Okay, think. Calm down and think."

Teleportation. That had to be the answer. He had studied some theories about it in the past, had even worked with some potential models on paper. That research had always been overshadowed by work on the time machine and on Reset. It hadn't been important enough to devote real energy to. What's more, it had never actually seemed to be possible, at least not with current understandings of science. Magically, perhaps. Temmies always seemed capable of teleporting, though they kept their secrets.

This was too much all at once. A few minutes ago he had been falling into the Core.

"Just—one thing at once. Deal with this first. Core, the doctor, later."

He had to get back home. Papyrus was the priority right now. He looked toward Snowdin again. It was about a half mile away, and the ferry stopped just north of the town. An hour's trip and he'd be home. This was fine. He could deal with this. Maybe in town he could even find out what day this was. Or…what year.

What year was this? If he had Reset, how far back had he gone?

The panic returned. He could be years in the past. Decades. Papyrus might truly not exist at all.

"Oh god, okay, no, don't think about that. You d-don't know anything yet." He gave a shaky sigh, looking down at himself. His bones were bruised and scuffed, his clothes torn. He looked like he'd been in a fight and had lost badly.

Lost. Sans started laughing, feeling almost hysterical.

"You're a mess, Sans. Look at you. Might want to stop talking to yourself, old buddy. Makes you sound kinda…"

He started to raise his hands to his face and stopped when he saw they were still shaking. There was a faint bluish light weaving through his fingerbones. The vibrating sensation was coming back, rattling his teeth.

"No, wait, stop."

He curled his hands into fists. He whipped his head around, frantic. If he teleported again, there was no telling where he might end up. There had to be something he could do, something he could hold onto…

There was nothing but snow around him.

"Just stop, just—"

The world blurred around him and Sans felt himself wrenched out of time and space. There was that dark place again, then Sans snapped back into existence. There was the popping sound of displaced air.

He sank to his knees, sick and dizzy. Ankle-deep water splashed beneath him, soaking through his shoes. The light was dim and something smelled rather foul. Sans clutched at his head, willing himself to stay conscious.

Once the world came back into focus, Sans looked up. There were massive piles of garbage all around him. This was the dump in Waterfall, where trash from the human world was swept down into the Underground via the rivers. Sans had come here once with Alphys. The place smelled terrible, but it was incredibly useful for gathering materials.

"Great," Sans muttered, voice hoarse. "In with the rest of the trash."

He dragged himself to his feet, swaying but managing to keep his footing. At least he was closer to New Home now. The ferry stopped a few caves away; maybe he could reach it before he teleported again. He chanced a look down at his hands. They were shaking, but it was the normal sort of shaking that came from fear and exhaustion.

This might continue forever, or until Sans vibrated out of time and space entirely.

"Just…have to figure out how to control it. Maybe…if I can just get back to the—"

A voice came from behind him, cutting him off.

"…hello?"

Sans spun, panicking.

"Stay back!"

He summoned his bullets without even thinking about it. The force of his own magic knocked him backward into the water. Bones exploded from the ground in a wave and kept going until the wave impacted the cave wall. Trash and water flew everywhere.

In the midst of it all was a small, floating ghost. The bones passed right through it.

"…oh…"

A split second later, the bones all vanished. Sans sat up in the water, eyesockets wide.

"Oh god, I'm—I'm so sorry I—I didn't mean to—are you okay, I—"

"…oh….I'm sorry…I must have interrupted you…oh no….I'm sorry…"

The ghost started to fade out.

"N-No, wait!" Sans reached out a hand toward him. "Wait, I'm…I'm sorry, I…I don't know how that…"

But the ghost was already gone. Sans dropped his hand to his side. The ghost had seemed unharmed—it was almost impossible to kill a ghost monster—but Sans had never used magic like that before. He had never summoned his bullets without meaning to. If that had been any monster other than a ghost, they would have been dead. How was this possible? His magic was powerful, but not nearly that powerful. That was magic on the same level as G…

He'd almost had it that time.

Sans stared at his hands again. Teleportation, and now increased magic?

"What's…happening to me? What did you do to me, Doc?"

The vibrating sensation started creeping through his bones.

"No, no, not again. No, please. Just stop, just h-hold still. Just hold still."

He squeezed his eyesockets shut as the vibration intensified. If he could just understand this, if he could just figure out how to hold still, then he might be able to control it.

"Hold still, hold still, hold—"

There was the wrenching sensation again, the feeling of going sideways. Sans tried to focus on it this time, the feeling of spacetime bending around him, the actual physicality of it as he traveled.

The world coalesced again and Sans reappeared in another area of Waterfall. Dizziness overtook him and he went down, curling on his side in the dirt.

"Okay," he breathed. "Okay. Just. Stay here for a second."

He lay in the dirt, closing his eyes again as the world wavered and spun. For several long moments, he just breathed. He was so tired. If only he could just fall asleep right here, and then wake up and have it all be just a nightmare.

Eventually, he rolled onto his back and stared up at the cavern ceiling. This was one of the narrower areas of Waterfall, affording him a view of the dim rock above him. This cave was small. There was nothing back here but a single echo flower and a bench, for some reason.

"You're gonna teleport into a wall if you keep this up," he said to the ceiling. "Then you can be a fossilized skeleton. Heh."

"Then you can be a fossilized skeleton. Heh," said the echo flower.

"Ugh."

"Ugh," the flower agreed.

He draped an arm over his eyes. Soon he would teleport again. He had to try and think before that happened. It was hard to think when he was this tired and this scared, but he had to at least try. This was going to kill him if he didn't get the hang of it.

The machine had done this—that had to be the answer. When he and…the others had been testing it, the machine had always generated a lot of excess magic that left any test subject practically humming. It was like the experiment they had done a few years ago, when the Doc had tried to strengthen Sans's soul. The same general principle: pump something full of magic and hope it didn't melt or explode.

That might explain why it had been so painful when the machine had activated. Sans shuddered a little.

The machine filling him with extra magic couldn't be the whole story, though. It explained why his bone bullets had become virtually uncontrollable, certainly. But the teleportation was a bit more complex. Sans remembered that at least two of their living test subjects had vanished into thin air. It wasn't just a matter of magic. The whole purpose of the machine was to unhook from the spacetime continuum and travel somewhere else. Time travel was a form of teleportation, in some senses. You couldn't travel through time unless you could also move through space. Otherwise you would end up time traveling right into the vacuum of space while the planet itself spun away without you.

"At least getting stuck in space would be pretty interesting for a few seconds," he muttered. The echo flower voiced its agreement.

The machine had unhooked itself from spacetime as it was supposed to, but it seemed that it left permanent effects on any subject inside at the time of activation. Or maybe it was specifically because the machine had in fact passed through the void beneath the Core. Sans frowned, trying to remember what that place had been like. He had been focused at the time on the light and magic and pain inside the machine. He remembered a feeling, or a sound maybe, like something had shattered. Like space and time had fractured into pieces. He couldn't remember anything after that.

Somehow, he thought that that part wasn't supposed to happen. The void had been a…he tried to remember. The doctor had explained it to him, but it was so hard to recall. A pathway. A pathway into the past. If such a pathway had broken while Sans was traveling through it, then…

Sans had no idea what that could mean.

The vibrations were starting again. Sans curled into a tight ball.

"Don't panic. Stay calm."

He dug his fingers into the dirt, as if hanging onto the world would keep him in one place.

Think. Focus. Pay attention.

It was a vibration. That had to be significant. Vibration, oscillation, resonance. Frequency, amplitude. Maybe he could think of it like…like tuning a radio or a television. Find the right frequency and—

"Hotland. G-Go to—"

Hotland. Heat, magma, the Core, the lab. Long nights spent working on the machine, on Reset. The terrible coffee in the basement, the good coffee in the chemistry department. The human souls glowing in their sockets on the wall. Falling asleep at his desk, waking to find someone had draped his lab coat over him. The permanent green stain on one wall of the locker room. The doctor, and other people whose names he didn't remember.

The world snapped out, then snapped back in. Sans found himself staring up at another cavern ceiling, this one high enough to be lost in darkness. There was a familiar warm, orange glow all around and the clank of gears nearby.

Hotland.

"Okay. Okay, good."

Sans waited for the dizziness to pass before taking a look around. He froze. He was on a small ledge overlooking a river of magma at least three hundred feet below.

"Hhhh…"

He scooted backward very carefully until he was secure against the cliff wall.

"Yeah, let's. Not teleport into the magma. Let's try to avoid that."

He couldn't see much above the cliff, but on the opposite side of the chasm was an area he recognized. Further along the chasm was a well-used bridge, the one everyone used to get from New Home to the laboratory. The lab had to be on the cliff above him, maybe half a mile away.

"Okay." He drew his knees up to his chest, trying not to look down at the magma. "You got pretty close, so…you're onto something. Right? Like tuning a radio. Heh. Complete with horrible static."

Every successive teleportation was more taxing, though. He had proven that he could control it, if only partially. Now he needed to figure out how to stop it from happening at all.

"Too bad I'm not a radio. Could just switch myself off. Hah." He folded his arms over his knees and let his head rest against them. "God."

The heightened emotions couldn't be helping either. He had been in a state of panic or near-panic each time he had teleported so far. If only he could just calm down.

He thought about resonance again. It wasn't just science. Magic came down to resonance as well. Spells and bullets were your soul resonating at the right frequency with your own magic. Almost all monsters understood that intrinsically, without ever needing to learn how it worked—but not Sans. He had only been able to fully utilize his magic for the past few years. Once the doctor had augmented Sans's soul, it had become easy. Sans could use his magic without thinking about it, like most monsters—but Sans always thought about it. His magic was always purposeful. He had to think about it, because if he didn't, then he would start to take the magic for granted.

Sans had never told anyone, not Papyrus, not the doctor, but ever since the experiment he had kept a certain understanding in the back of his mind. Just because the experiment had worked didn't mean it would work forever. There was always the chance that one day the extra magic would simply overwhelm Sans's weak soul. It could shatter his soul and kill him, or it could simply fade, leaving him as powerless as he had been for most of his life. Sans didn't want to die, and he couldn't even imagine going back to that kind of life. So he was always cautious with the magic. Always purposeful. He always exerted exactly as much effort as was necessary, and never a drop more. Even though the magic had never caused him any undue stress or alarming effects—at least until now—he was still always careful. Most people called it laziness. But when you went through life with 1 HP, having to rely on luck, speed and cleverness just to survive, you learned to be careful.

Or you died.

If he could understand normal monster magic with that kind of mindset, then he could understand this. Resonance. He thought about what it felt like to not use his magic. To be able to do something, but to hold back. To do nothing.

He had always been good at doing nothing.

"Hold still."

He could sense the vibration starting again. Fear curled in his ribcage, but Sans drew in a slow, deep breath.

"It's okay. It'll be okay."

It came on slower this time. The vibration was less violent, less frightening.

"Let's try to aim." He drew in another breath. "Okay. Papyrus. Wait—wait, no."

If he tried to teleport directly to Papyrus, he would scare the daylights out of his brother at best and atomically fuse with him at worst. He was pretty sure that would kill them both. Assuming Papyrus existed at all.

"Nearby. New Home."

He slipped sideways. A moment later, he reappeared—not fused with his brother, or a wall, for that matter. He slumped against something solid, blacking out for a few seconds.

When he opened his eyesockets he found himself in an alleyway, in between two garbage cans.

"Back with the trash," he said, smirking. "Think the universe is trying to tell me something."

He could see the street from here. Across from the alleyway was a convenience store that he recognized. A smile blossomed across his face. He'd done it. He was less than a block from his apartment.

He tried to stand, failed, tried again. Bracing himself against the brick wall, he pulled himself to his feet. Then he started to very slowly make his way to the street.

The street was deserted. Maybe he had gone so far back in time that no one had moved into this part of the city yet. But no, that didn't make sense. That convenience store had been there for only about ten years. And that little clothes shop further down the street, that had opened only a few years ago. That meant that Papyrus must still exist. Right?

Sans told himself not to get his hopes up.

He stumbled off down the street like a drunk. The apartment building was in sight, but the whole world was swimming, and Sans could feel himself starting to vibrate again.

"Come on. Please. Not again. I just want to see him." Sans leaned against a shop window. "Just let me see if he's there."

But fighting it hadn't worked thus far. In fact, it only seemed to make it worse. Sans kept walking and focused. It was like with light blue attacks. You just had to keep still. You just…

Now there was an idea.

Sans stopped and held onto a street light with one hand. The other he laid flat against his chest. He reached for his magic, braced himself, and turned his own soul blue.

Ding.

The experience of grabbing his own soul was unsettling and horrifying enough that he almost let go. There was that all-too-familiar heaviness on his soul, only this time he was the one holding it.

A frightened, disgusted sound escaped him. He hated this feeling. It reminded him of…

G…Ga…

Not quite.

"He turned my soul blue a few times." He could remember that, though he couldn't remember why, or what the context had been. "Sounds like he must have been a jerk."

It was unpleasant as hell, but it had worked. He hadn't teleported. The vibrating had stopped. He was still in New Home, just half a block from his apartment. From Papyrus.

Sans released his soul, took a shuddery breath and kept walking.

He made it to the front door without collapsing, and without the vibration coming back. Then he was faced with two flights of stairs. It took another ten minutes just to get to the third floor, clinging to the railing the entire time and almost passing out when he reached the first landing.

The vibration started to come back as he rested at the third floor. He waited. It was far less intense this time. Teleporting seemed to take quite a lot of energy; perhaps his body was simply out of juice. He stood still, breathing, thinking about blue and light blue attacks, thinking about resonance.

It was painfully slow, but the vibration subsided. Sans almost dropped right then and there from relief.

Instead, he dragged himself to the door of his apartment. Moment of truth. He went to dig out his keys, only to remember that his keys were in his bag. Which was still back at the lab. He had left the lab intending to be back in an hour or two—then the doctor had decided it was a great time to destroy the whole world and pilot an unstable machine through a hole in spacetime. Sans hadn't exactly had the opportunity to return to the lab for his stuff.

Of all the stupid things.

He raised a hand and hesitated.

Maybe there was no one living here. Or maybe it was a stranger. If he knocked and a stranger answered, Sans didn't think he would be able to take it.

He knocked.

And waited.

Nothing happened.

"No, please."

He pressed his forehead to the cool wood of the door for a moment, then knocked a second time, louder. He was shaking again, but not from vibrations.

"Please, please, please, don't do this to me, please—"

There were footsteps from the other side of the door. Sans's breath caught in his ribs. The door opened.

And there he was. Looking more irritated than Sans had ever seen him and wearing bunny-patterned pajamas.

"ExCUSE me, but do you have ANY idea what time—" Papyrus stopped, and his face went through so many expressions so fast that it would have been comical any other time. He settled eventually on horrified confusion.

"Brother?"

Sans said nothing, staring up at him.

"My god, Sans," Papyrus said, his voice hushed by Papyrus standards. "Do you have any idea how WORRIED I've been? Do you know how late it is? You didn't call! I thought you said you would be home at a NORMAL hour! I tried calling you and you didn't answer!"

Sans blinked stupidly. He reached into his pocket for his phone, noticing too late that his pants were waterlogged. The phone was dripping when he pulled it out of his pocket.

"What in the WORLD happened to you?" Papyrus ushered him inside and closed the door. The apartment looked the same. Exactly the same as when Sans had left this morning.

"You're soaked! You look like you've been rolling in the mud! Oh dear, you didn't track mud all the way up the stairs, did you? The landlord will yell at us again. Sans, what have you been DOING? And why did you knock? Where's your key?"

"P…Papyrus…?"

His voice sounded broken, even to Sans. All of the irritation and confusion on Papyrus's face was immediately replaced with concern. He couched down and took Sans by the shoulders.

"Brother, what happened? You're shaking. Please, Sans, you're scaring me."

"I…s-sorry, bro, I…didn't mean to…wake you."

"Sans, I hardly care about that right now! Just tell me that you are okay."

Sans reached up to cradle Papyrus's face in his hands. Papyrus was the same as Sans had left him. He was real.

The weight of everything hit him all at once and he sagged.

He wrapped his arms around his brother and buried his face against his chest. Papyrus embraced him tightly.

"Sans?"

"I'm sorry," Sans choked out, squeezing his eyesockets shut as he tried to hold back a sob. He wasn't going to cry. Not in front of Papyrus. Papyrus was worried enough as it was. "I'm s-sorry, I didn't… I'm okay. I'm fine. It's fine. Y-You don't need to worry…it's…I just had a long day and I'm s-so glad you're here, I was…scared you were…"

"Oh, Sans…" Papyrus held him tighter. "It's alright now, brother. Whatever it is, it's alright now. I'm here."

Sans clutched at Papyrus's pajamas. A small whimper escaped him. Then a sob. Sans gave up and did something he almost never did.

He let himself break.

He sank to the floor, sobbing into his brother's chest. Papyrus went with him, holding him tight, trembling a little. Sans had to be scaring him, but he couldn't stop.

"Shh, it's alright," Papyrus said, cradling the back of Sans's skull with one hand. "I'm here."