Summary: When an outside force messes with the timelines of Undertale, the genocide and pacifist route become one, Leading to disastrous consequences. Frisk and Chara must put aside their differences and work together to return to their respected timelines or it could mean the end of everything. However, dark forces are working behind the scenes to make sure they never find their way back.
Disclaimer: I do not own Undertale all charters belong to Toby Fox; all AU characters belong to their respective creators. I hope they don't mind me using them. If anyone thinks I've written any of the characters out of character, please do let me know. This is my first Undertale fic, however I did start this a few years back but stopped it because I didn't know where it was going but don't worry I won't be making that mistake this time as I have improved sense then and have planned almost the entire story out. I was inspired to write this thanks to a fan comic called SwapTale (I don't know the creators) and the very popular Undertale animation on youtube Underverse created by Jael Penaloza. Though I do hope my story won't just turn into a copy and paste of her work and can stand out as something different. Now on with the story…
Save or Kill
Chapter 1
The small chubby skeleton stood his ground as he waited for the human to Reset, the golden tiled floor had been stained with so much blood and the pillars had been knocked down and crumbled into piles of rock and debris. The last battle had taken quite a lot out of him, and he had resorted to swinging the child around like a rag doll smashing the pillars into pieces as their lifeless body flew through them. Though the tired skeleton couldn't help but laugh because in the end It didn't matter. No matter how many times he hurt them or how much effort he put into killing them. They would always come back and every time they walked down that corridor with there dusty knife in hand, the wounds he had previously inflicted on them gone. Each time they Reset it all cleaned it's self-up, not a single drop of blood had been spilt on the shining golden floor and the pillars were of course intact as if they had never been broken in the first place.
The small skeleton kept his bony hands inside the pockets of his blue hoodie, he wore a white shirt covering his ribs and spine. The all to familiar creaking of the door, alerted the skeleton, letting him know that the next battle was about to start soon. He let the grin grow across his face as he glared at the small human child standing in front of him. The human ignored him and moved towards the box beside them, rummaging inside for a weapon or healing items. The skeleton took this moment to relax and think back on the events that led him to this moment. It all started with a promise, a promise to protect the human, a promise he wishes he had never made. After they made it out of the ruins he met them, they were covered in dust, monster dust. Straight away he knew they had killed someone but he wanted to believe it was self defense or an accident. That was his first mistake, he should have just taken them out then, if he had done that then…
Save
The human advanced towards the skeleton, who could only let out a forced laugh in return. "I guess I should congratulate you, this will be your 100th time dying" Sans laughed, his left eye glowing blue.
The human was the first to attack, they swung their knife down towards the skeletons belly, then jumped up in the air. While they were in the air, Sans summoned a swarm of blue bones behind them but they managed to doge past each one of them as they dashed forward. They landed in front of Sans and as they got up they quickly swung there blade towards his neck. He was only a few seconds away from death but luckily managed to avoid the knife for what felt like the 1000th time. Teleporting next to them, his left eye glowed with a furious light blue cinder as he began summoning Gaster Blasters. One after another popping up from out of nowhere, encircling the human child. They looked flustered and panicked, as they frantically looked around for a chance to escape. The skeleton let out a small laugh as he clicked his fingers, on his mark the Gaster Blasters simultaneously fired a long blue beam of light towards the child.
The impact of the blast caused a huge smoke cloud to surround the room, Sans scanned the room carefully. The smoke cloud served as both cover for him and the human, as time passed he felt himself grow nervous and cautiously summoned small army of bones beside him. That was when he felt it, if he had hair it would most definitely be standing up, a warrior's instincts is what his friend called it. Without hesitation he swung himself around and stretched his arm out catching the humans soul. A few seconds slower or if he hadn't alerted himself to the humans sneak attack, then there knife would have most defiantly pierced straight through the back of his skull.
He caught his breath as held them tight in his grip, he couldn't allow himself to think about what could have happened. Instead he threw the human into the columns, there bones breaking as the arcuticure fell apart on impact. Then he forcefully dragged them back and smashed there body through the columns on the other side. He repeated this attack over and over again, there blood staining the once golden floor. Once the human stopped resting, he slowed down and eventually stopped, holding the human still he breathed heavily as they laid there no longer moving, no longer posing a threat.
Finally is it over
Before the battle Sans was happy, well as happy as one can be when they know things they really shouldn't. However, they had friends, a fire monster, bartender who listened to there woes and made sure they were feed. A mysterious lady, who lived on the other side of the door leading to the ruins, who made Sans tiny monster heart flutter every time she laughed at one of his terrible jokes. His former co-worker and respective scientist, who always helped him make sense of things he could never make sense of himself, even if she didn't truly understand. Even his brothers friend helped Sans from time to time, though they didn't always see eye to eye, he did respect her sense of justice. He'd like to think that was why he was here today fighting the evil human child but in all honesty it was only because of what happened to the most important person in his life. His brother, the reason he hadn't given up on this world long ago, the only person who can truly make him smile.
These people meant the world to Sans, each of them were a light in his eye sockets and while he may have valued more than others. He never wanted this for them. Who could have known that one day a single human child would fall into the underground and extinguish all his lights.
"Augh!" Sans snapped out of his thoughts as a sharp pain ran across his chest.
The human had been playing dead the whole time, Sans could only laugh, he let himself get distracted and now he was going to die. He winced as they pulled the blade out of his stomach, he dropped to one knee, tears swelling up in his eyes. He knew he had failed, that the child would go on to kill the king and then probably the humans but he couldn't help but smile. Now standing before him in his final moments were all his friends welcoming him to join them and in front of them was his brother.
"Pa-Papyrus"
The human looked back at the skeleton, they felt nothing, no guilt, no remorse, nothing. They had a job to do and he was standing in the way but even if he wasn't he would still have to die. Even the monsters who have evacuated the underground will eventually be hunted down and killed. That was there job, there goal, there only purpose in life. Killing, it's the only thing they know how to do, the only thing they were told to do sense they were awakened. The skeleton still lived but not for long, still even though the human realized this they couldn't help but watch, the skeleton was unlike the others before hand. He had killed them again and again, successfully blocking there path for a very long time so as he lay there dying they couldn't dare tare there gaze away.
Then something strange happened, although neither the skeleton or the human was aware of it at the time. There fates were being re-written, a small change to affect everything. The change in question remains a mystery just like the one behind it all.
The skeleton could feel himself falling apart but he didn't fight to survive, there was no point, everyone he ever loved and cared about was dead. Why bother living in a world like that. "Papyrus, I'm coming" Sans whispered, then fell to floor.
He should have died and turned to dust, after that the human would have killed the king and there former friend. They would have gone on to hunt down and kill every last monster before turning their attention to the rest of the world. That's how the story was meant to go but now things had changed and Sans could feel someone healing him.
Authors Note: Hello I hope you enjoyed the beginning of this story, this is my first time writing a Undertale fan fiction outside of my crossover. I don't know when the next chapter will be but if chapters stay short like this then i'll try and post at least twice a week. Anyway, I don't have much more to say other than that, please favourite the story if you like it, follow to stay up to date and leave a review letting me know what you think.