To The Bone: Undertale Fanfiction

Prologue

Front cover by Inky Chan

Warning: This book contains spoilers of the game Undertale, I advise you to play the game first!

Or you can just go through the book I don't care.

Sans was walking through the lab, looking for Gaster. he's probably working on the machine... Sans thought. Gaster has been building a machine that can give a monster's soul DETERMINATION, like a human. But Sans was against that idea.

He found Gaster working in his private lab near the core.

"Oh, there you are Sans", said the scientist, "can you help me with something?'"

"* If it's for that, no." He responded, pointing at the machine. "* I told you, it won't work."

"It's almost done, I just need to do something," Gaster told Sans, ignoring his response, "can you hold this please?"

The scientist nodded at some gadget, Sans grumbled and held it. Gaster started connecting some wires to it. While he did that, Sans observed the machine; there was lots of progress since the last time he saw it, it gave him the creeps, who knows what could happen if that thing was turned on? It could explode the whole lab and everyone inside it would fall into the Core. Or worse, the whole Underground.

"* You don't get it, do you?"

He ignored Sans again, and took the gadget from him and fixed it onto the machine. Sans folded his arms, shaking his head. Gaster stood in front if the machine, his hands on his hips.

"Mission accomplished." he said proudly.

Sans froze, with a weird expression on his face.

"* U-uhhh, what??? In two months?? Are you sure..?" He asked nervously.

"Yes I'm sure." Gaster gave him look of annoyance, then turned back to the machine, "I'll just test it and see if it works with Core power."

"* Core power?!?" Sans repeated "Are you out of your mind?!?!?"

Gaster rolled his eyes, When you roll your eyes like that, Sans thought, I assume that your looking into you're mind for an adequate response and coming up empty. The scientist started doing stuff on the machine's computer, and pulled a lever. The machine began to do some slow beeping noise, Gaster looked up and waited, the noise stopped, then there was weird mechanical whirs coming from the machine. He looked confused.

"* Is this supposed to be happening..?" Asked Sans

"No..." Gaster responded, "something's wrong..."

He began doing something on the computer, then an alarm sound started and the machine's screen flashed red. The ground started shaking, objects started falling from shelves which making lots of skull rattling sounds. Sans rushed to look at the Core; it was getting unstable. Sans turned to Gaster:

"* The Core is getting unstable! We need to stop it!"

The ground shook harder. Afraid of accidentally falling into the Core, Sans moved away from the edge and tried to stay balanced. But Gaster was still working on the machine, which was very close to the Core. The ground bounced, sending the two skeletons three meters from the floor into the air. Sans landed on something sharp, sending a jolt of pain in his arm. Luckily he still had 0,5 HP/1HP. The other, almost fell off, he held on to the edge.

"Sans!!"

"* Gaster! Hold on!"

Sans struggled to get up, the floor quaking, he ran to the scientist, clutching his arm. He knelt down and tried to pull him up, but the ground shook again violently and Gaster fell off into the Core...

"* GASTER!!!"

Sans watched in shock as his friend fell. He stayed there, his jaw trembling. The ground still shook, Sans grunted and shot a bone at the stupid machine. Slowly the shaking stopped.

"* Y-you idiot!" Said Sans, his voice trembling, "Why didn't you l-listen??"

~
Days have passed since the incident, as Gaster fell into the Core, everyone forgot him, as if he's been erased from this timeline... Only Sans remembered, it haunted him. After all that happened, Sans decided to resign from his job at the lab and moved to Snowdin with his younger brother, Papyrus. He brought the machine with him and tried to fix it and undo what happened, but never succeeded. After two years of trying, he gave up...