Long ago, two races ruled over Earth: HUMANS and MONSTERS. One day, war broke out between the two races. After a long battle, the humans emerged victorious. They mercilessly drove the monsters off the surface, sealing them underground with a magic spell.

One way in. No way out.

After many year the monsters yearned to return to the surface. But it was impossible for anyone to cross the barrier.

Except, perhaps, the last of the Time Lords.

I gave a small growl of frustration and slammed my hand against the side of the strange metal box. The squiggly lines wavered for a second before clearing into something that would only make sense to a time traveler.

Someone, something was messing with time. Timelines were jumping back and forth, straining the time-space continuum. My research had led me to a strange place called the the Underworld, a place inhabited by all sorts of monsters. From what I could see, the time anomalies had started in a specific place called "Judgement Hall".

I scrubbed a hand through my spiky brown hair as I gazed up at the yawning archway that led to this "Judgement Hall". Then I took a breath... and stepped inside.

Golden light streamed from enormous gothic windows set in the wall, causing the pillars to cast long, slanted shadows. It was empty of life except for a small round skeleton, standing in the middle of the hallway. He wore a blue coat with a fur lined hood, and black shorts. Pink slippers rested on his feet. It would have made a for a comical appearance, if his expression hadn't been so stony. I stepped forward, raising a hand in greeting.

"Hello there, I'm the Doctor," I greeted with my usual cheer.

The skeleton's face bore a casual smile, but I could feel the white orbs in his eyesockets scanning over me. "hey. i'm sans. sans the skeleton. you must be looking for king asgore, right? he's in the next room."

"All right, then. Brilliant," I told him, but my tone didn't match my words. I held his gaze steadily, scanning him just as he scanned me. Finally, I broke the contact, and began walking away. Perhaps this King Asgore can give me some answers.

"it's you. you're the one who's been causing all this."

I stopped mid-step as the words reached my ears, then slowly turned around to see Sans staring at me.

"Um... what?"

"this all has to stop." His gaze looked through me, and his voice abruptly deepened. "do you wanna have a bad time?"

For a second I stared at him, my mind flicking over the various possibilities of what he could mean. Then I glanced down, clearing my throat. "Um, I... I guess that depends on how bad a time you want, Sans-y boy."

He didn't answer me, but kept the grin on this face. One eye socket burned black, the other flickered blue. "you've reset the timeline one too many times." Then he raised his hand and a large mammal-like skull materialized.

I opened my mouth to speak, but then thought better of it and dove out of the way as the skull opened it's mouth and blasted out a stream of white flame. A second later four more appeared, replacing the first. I managed to scramble out of the way, but tripped over a stream of bones that had seemingly come out of nowhere.

"you started this time loop, didn't you?"

The skeleton flicked his hand and another row of bones barreled towards me. I jumped to my feet and leaped over them, landing hard.

"the same couple days. the same brutal murders."

More skulls, more fire. This time I was a second too slow, and the flame ripped through the sleeve of my coat, burning my arm. I stumbled, then gritted my teeth against the pain and tried to recover. At that moment, a blast of flame shot me right in the chest, slamming into one of my hearts. The impact threw me to the ground, and carried me several feet across the smooth floor.

"all because of you." Each word was drawn out, slicing through the air.

A small hiss of pain escaped my lips as the agony spread through my body. For a moment I simply lay there, gasping for breath. Then something stirred inside of me.

Determination.

"How... how do you even know about the time anomalies?" I gasped, heaving myself up. My entire body was shaking. I placed a hand over my chest, and felt wet blood start to trickle through my cracks between my fingers.

The skeleton said nothing, but simply continued to smile, his eye flickering with an outline of blue. My determination slowly faded under his gaze. "I swear, I'm not the one doing this!"

He didn't answer, only swiped his hand to the left and slammed my body into a pillar. I hit the floor with a thud, struggling to breathe.

I forced my eyelids open and saw pink slippers in front of my face. I lifted my gaze and saw that both of the skeleton's eye sockets were dark.

I felt something pulling me up to my feet, but I could not stand. My legs would not hold me, and my knees hit the floor with a crash. The skeleton raised his hand, a skull materializing just above it.

"die."

I simply stared at him, my breath shuddering, my hearts sinking. But not simply because I was about to die. Because something was hurting this world, and there was nothing I could do to stop it.

"No, Sans, stop!"

It was a child's voice.

The light suddenly returned to the skeleton's eyes, and he slowly closed his hand, the skull dying away.

I slowly let out a breath, and let my body slump forward onto the tiles, my eyelids flickering. The patter of small feet grew louder. I wearily lifted my gaze to see a small human child with dark brown hair and rather squinty eyes come running up.

"kid..." the skeleton was breathing hard, sweat dripping down his skull. "what are you doing here?"

"Sans! What are you doing? Why are you hurting him? This isn't like you!"

The skeleton looked as if he were about to protest, then, suddenly, his expression seemed to crack. "frisk... oh my gosh, frisk..."

"Sans." The girl stepped forward. "I know you. You're the one who taught me to show mercy. I mean, you don't have a bad bone in your body."

"heh..." The skeleton's voice came out so soft I could barely hear it. "i... don't know about that, kid..."

The pain was making my vision blur. I tried to roll onto my side, balling up the end of my coat to press against the wound, but the floor rocked violently. I closed my eyes and let out a hacking cough, sweat dripping from my forehead. Just then, a bony hand closed around my shoulder and looked up to see the swimming face of Sans.

"call papyrus and undyne," he said to Frisk, his voice tight. "alphys too. tell them to hurry."

"Got it."

The skeleton gently pried my bloodstained hand away from my chest and pressed a wad of cloth against the wound.

"i... i'm sorry," he told me quietly. "you had nothing to do with this, i... know that now."

"Don't... worry," I coughed, the edges of my vision darkening. "You're not... the first person who's... tried to kill me. But… why...?"

For a few moments the skeleton didn't answer.

"something kept killing all the monsters down in the underground... like a genocide. the worst thing is, it, whatever it was, wasn't content with killing us once. we kept going back to the time where the murders started and no one but me would remember what had happened. i had to watch my brother, papyrus, had to watch everyone, die over and over again. finally, something inside me snapped. i saw you and all i saw was another human, someone who was screwing with the timeline, someone who was going to kill us all. but then... when frisk came, i remembered. i remembered how she had not only shown mercy, but had gotten us all out of here. before it just looped back or whatever."

"Sans," I whispered. "I will fix this. I promise."

"heh," the skeleton gave a dry laugh. "have to admit, i never really liked promises."

Silence slowly covered the Judgement Hall. The golden light washed over us, the Time Lord and the skeleton, two time travelers who had seen too much.

Minutes, perhaps hours later, the air filled with the pounding of feet.

"O-oh d-dear, that's a-a lot of b-bl-blood."

"WOWIE! IS THAT ANOTHER HUMAN?"

"Hey, back up, you guys! Give the man some space!"

"It's all right, Mister, it's gonna be okay," I heard Frisk say, just before the ground beneath me faded, and darkness fell.