As much as Sans despised the timelines resetting, there was one thing he didn't actually mind too much. The human had reset again, but Sans had lost track of how many times it had happened.

Although he despised it, he did like watching the timelines reset.

The time flowed backwards, like a river in reverse. He let his finger dip into the liquid time and smiled sadly as the moment rippled and continues its adventure. Each time was a little different, each timeline tinted red or blue or purple or a mix of all the colors.

Sans sighed sadly, watching the happy timeline reverse into something unknown. Something moved in his peripherals, and his head shot up. No one had ever joined him here before. He focused his eyes in the distance, but only finding shadows.

He glanced back at the time line and saw black snaking its way through the colors. His vision snapped back up, and widened dangerously. In the shadows was a figure, a tall figure. It was barely there, the body more shadow than actual being.

The shadow being took a step forward and held out a hand towards Sans, the white limb had a large hole in the palm. Sans wanted to take a step back, but found himself frozen in his spot. The figure took another step forward and the short skeleton was able to make out its face.

A sad smile, a few cracks. They were familiar, in an unfamiliar way. They moved closer yet again and let their own fingers dip into the stream. Instantly, black flooded the colors, disporting the moments and memories.

"What are you-" Sans stopped himself. The figure seemed startled at the spreading darkness. "G-Gaster?"

The name came to Sans like a distant dream, barely making any sense. The figure looked up at him and gave a strange smile. The figure – Gaster - reached his hand out to Sans, as if to touch his face, but more of the blackness dripped into the stream, causing the colors to splash up and spill over the edge in a murky puddle.

"D-don't!" But it was too late. The stream was contaminated. Sans had no idea what that meant, but it couldn't be good. Gaster made a low keening sound and tried to scoop the black from the timeline, only succeeding in making the moments even darker.

"Sans… fix it?" His voice was low and grinding, the familiarity making Sans flinch.

"I… I don't know how!" Sans was sweating, his eyes wide.

"Play… game… yourself." The shadows spoke for Gaster. "Destroy… hate."

The world began to tilt, the indication that the timeline was almost done resetting. Sans frantically looked around, trying to save the timeline.

"Gaster what do I do?" He began to cry a little. The shadow man reached out and smudged his thumb across Sans' forehead. He felt something cold on his skull before the world gave a violent jerk. Sans was thrown to his knees, and his eyesight went dark.

Sans was kneeling in the snow, the cold not yet chilling his exposed leg bones. He stood shakily, already noticing something majorly wrong. He never woke up in the snow. The world always restarted on the fifth of December. Papyrus always called to him as soon as he woke up, calling him a lazy bones and reminding him to put on a jacket before going out.

But not this time. Sans tried to remember what happened, but it was so vague. He was looking at the timeline, like usual. But this time there were shadows everywhere. Shadows on the walls, shadows in the timelines. There was a growling voice, but no words to connect it to.

Sans brushed the snow from his shorts and tried to figure out where he was. Looking directly behind him, he noticed a large locked door. It was almost identical to the one back in the last timeline, but this one was more worn.

Chips in the stone disfigured the designs almost completely. A large crack ran across one of the sides, and the ground was littered with snow covered debris. As Sans was trying to figure out why the door was so destroyed, it opened slightly.

A small figure slipped from the crack, their sobs echoing through the snow. Sans followed them. He would call it muscle memory, if he had any muscles. His magic stopped them at the gate and turned them around.

"Is that any way to greet a new friend? Turn around and shake my hand." He held his hand out, and the human flinched away violently. Sans retracted his hand just as quickly. The kid was shaking like a leaf, and it wasn't just from the cold.

It was then Sans noticed something else about the child. They had a small growth perched on their shoulder. His eyes narrowed and his magic yanked the lump from their shoulder. The yellow flower floated in the air surrounded by a blue aura. The child cried out and jumped up to reach the monster, but Sans refused to let them be injured.

"Put him down!" Their small voice shocked him. They sounded terrified.

"I won't let him hurt you." They looked even more scared.

"Hurt me? He's my friend!" Sans paused. He glanced up at the glowing flower and saw shocked to see tears coming from his little flower eyes. Reluctantly, Sans lowered the flower back into the child's shoulder. The blue aura disappeared.

"What's going on here?" Sans wasn't buying it.

"I f-fell, and Flowey healed me! And he helped me get past…" They shuddered.

"T-toriel?" They flinched at the name. Something was definitely wrong.

"Yeah…" Sans covered his face with his hands. How had this happened?

"Alright Kiddo. Let's head out, there should be someone up ahead and I don't know how friendly he's going to be." They squeaked a little at his tone but grabbed his hand.

Sans and the kid walked through the bridge to the familiar clearing, but something was wrong. The lamp was smashed, and the sentry booth looked abandoned. A loud cackle sounded in the distance and Sans shoved the kid behind him.

"Come on out. We're not here to cause any trouble." Sans tried to sound relaxed and friendly, but an edge seeped into his voice. He heard a branch crack, and a softer cackle before a tall figure came into view. Sans almost collapsed right there.

"Papyrus?" The figure stopped walking for a second. He seemed…. Scared?

"B-brother?" Sans had never heard that amount of terror in his brother's voice before, and he hated it more than anything. He took a step towards his brother and finally saw him. He was the same height, maybe an inch taller, but somehow even skinnier. His Battle Body suit was pitch black and beaten up. The worst thing, however, was the crack covering this entire right eye.

"Pap…" Sans left the child and ran at his brother, needing to make sure he's okay. This Papyrus scrambled back and fell on his tailbone, causing Sans to stop dead in his tracks.

"L-look Brother… I'm so s-sorry I w-wasn't at my post. P-please give me another chance! I can p-prove it to you!" Sans stared at Papyrus with wide, frightened eyes. Even the human realized something was wrong.

"Papyrus… what's going on here?" Sans' voice was soft. He knew this wasn't his Papyrus, but he wanted to pretend for at least one second. Papyrus just gave him a confused look.

"I just… Brother are you alright?"

"Am I alright? Bro look at you! You fell in the snow!" Sans let his voice raise, and he realized a second too late what a mistake that was. Papyrus flinched violently and tried to move back even more. He was trembling. Papyrus was trembling… because of Sans.

"B-but… you threatened to… You promised I would regret slacking off again. That it would be even worse than … last time." Papyrus' voice cracked in fear.

Sans made it to his brother's side in two strides and fell to his knees next to him. With trembling hands, he reached out and barely brushed Pap's cheekbone. Papyrus was trembling even harder, his eye clenched shut in fear.

With a cry, Sans wrapped his arms around Papyrus' shoulders. He buried his face in his brother's shoulders and let only a few stray tears escape. Papyrus was frozen under his touch, afraid to move. After a few moments, the gloved hand reached up and patted Sans on the back twice.

"Who…who are you?" Papyrus sounded broken.

"It's me… Sans?" Sans stood and looked at his brother again. "God this is so messed up…"

"You are not my brother. My brother is…" Sans had turned away to face the kid, who had been standing silently behind them.

"Probably not very nice." Sans finished the sentence, not bothering to turn around.

"Is that… a human?" Sans froze, knowing that tone of voice. He heard the other skeleton stand and the telltale hiss of magic. Glancing behind him, Sans saw Papyrus with two dark blue bones in his hands. His good eye was narrowed.

Sans did what he knew he had to do. He summoned his own bone and blocked Papyrus' way. Papyrus stopped dead and stared at the bones with shock and…. Something akin to awe.

"Blue?"

"Bro you're gonna leave the kid alone, or you're gonna have to go through me." Papyrus ripped his eyes away from Sans' magic and stared straight through Sans.

"What are you?" Sans dropped his magic and held a hand out for his brother.

"Papyrus… we need your help. Something is wrong here, and I have to fix it." Papyrus hesitated before slowly reaching out and taking Sans' outstretched hand.

"Sans… what is going on here?"

"It's a long story bro…"

"We are…wrong?" Papyrus was trying to understand everything Sans just told him, but was having a really hard time.

"Essentially…" Papyrus scratched the crack over his eye and sighed.

"We need to find Undyne." Sans instinctually stepped in front of the child and their flower companion.

"Will she attack the human?" Papyrus' eye opened with slight shock.

"What? No! Undyne is the leader of the rebellion." It was the Sans' turn to widen his eyes in shock. Rebellion? What kind of world did he end up in?

"The what?" Sans was not sure what he wanted to hear.

"Erm… maybe it would be best if Undyne explained it herself." Sans nodded, wanting to get this adventure – or nightmare rather – on a role. Papyrus moved from behind the sentry station, where they were huddled to avoid the cold while Sans told his story. Papyrus pulled out a sleek black phone and hit a single button before holding it up to his skull. Sans turned back to the human and asked something that had been bugging him.

"So kid… what happened to you in the ruins?" The child grimaced a little, and the flower was the one that answered.

"The lady there… she was pretty nice at first, but said she had to take the human's soul before the monster king did. She said she would make it painless… that it had to be done. She didn't seem like she wanted to though…"

Sans connected what dots he had. It seems like this timeline was fundamentally the same, but something happened to change each of the monsters. Toriel must have needed to take the soul before the King, but why?

Papyrus slipped the phone back into his pants and waked over to the two monsters and the human.

"Undyne is thankfully in the area. She told us to make it to her home as discreetly as possible. If we go around Grillby's and make it to the River Person, they should be able to-"

"Don't stress bro. I got this." Sans grabbed hold of the Human's right hand and his brother's left hand before letting his eye glow blue. Papyrus breathed in sharply and muttered blue again.

Sans let the magic pulse though him and felt it flare across his surface. The human gasped a little and he let the magic snap. The world went dark, and when the world came back into focus they were standing on the doorstep of a fish shaped house.

Papyrus ripped his hand from Sans' and stumbled to the side, on hand steadying himself on the house and the other grasping his chest. He retched once and breathed heavily for a few moments. His breathing didn't calm, and Sans began to worry.

Just as the shorter skeleton was going to place a hand on his brother's back, the front door flew open. Sans found a spear in his face and a shiny arm wrapped around his brother.

"Step away…" She all but growled at him. "Papyrus you never said he was with you. You've ruined the whole rebellion!" Papyrus was still breathing heavily, but it had calmed down a little bit.

"W-wait Undyne. It's not him." Undyne spun to face Sans, her good eye burning with rage.

"Not him? Are you crazy?" Papyrus stood up straight and ran a hand over his skull shakily.

"Take a closer look." Undyne stepped closer and Sans felt himself tense up. He tried to keep his smile innocent, but he could feel the edges of it trembling. A cold, gloved finger rapped his teeth and he opened his mouth in shock. Undyne's finger tested his fang and as soon as the digit invaded his mouth, it was gone.

"Papyrus. Explain." He gestured to the front door with his head and she nodded. The two of them ushered everyone inside and Undyne locked the door directly behind them. She stared at Sans and the human until they sat at the kitchen table. She slammed her hands down on the table, causing the crack down the middle to grow. "It's obviously not him. This one's teeth aren't sharp enough, and his magic is blue. I saw when you guys got here…"

"This is not my brother, you are right. This is some… over version of him. Apparently the timeline he came from is much nicer that this one. Something happened during something called the Reset, causing the timeline to be contaminated."

"You." Undyne got Sans' attention. "Is this true?"

"Yeah Undyne. There's something seriously messed up here, and I have to fix it to get everyone back to normal."

"W-what's… 'normal' for us?" Undyne's voice was timid, afraid of what Sans would say.

"Well… my brother is a little goofy. He doesn't understand how the world really works, but he cares about everyone so much he's willing to try anything. Undyne is headstrong. She honestly believed in taking the soul of the human, because she wanted to free the monsters from the underground. She was adamant about capturing Frisk, but they befriended her and she became a good friend. She was the one who taught Pap how to cook, and had a big ol' crush on Alphys even if she refused to admit it. Alphys was a little awkward, and a lot of nervous, but she helped the human though all the puzzles and really saved their life.

"Toriel lived in the ruins and tried to prevent any humans from leaving so she could protect them from Asgore. The King was always a pushover, but he had to take the human souls to break the barrier, even though he hated violence. Mettaton just wanted to be a star. He tried to take the human soul too, but he realized he was needed in the underground more.

"On the other hand, Flowey was evil. He tried to kill Frisk as soon as they fell down. He followed them and tried to kill them in the end, which explains why I was so harsh when I first saw him on your shoulder."

Everyone was silent. No one knew what to say…

"Well… that time line sound much better than this one." Undyne had taken off her armor and rested her elbows on the table and her face in her hands.

"Now you have to tell me something." She looked up at Sans and didn't like the grin look on his face. "My bro said something about a rebellion. Now, something about that sounds weird."

"I-it's… it's a rebellion against…" She closed her eyes. "Against you Sans."

"Y-you gotta me kiddin me…" Sans wished with every fiber of his being that she was joking, but by the look on her face it was obvious.

"I wish I was. You- the other Sans realized just how powerful a human soul is, and challenged Asgore… and won. He could have gone through the barrier, but he wanted to make sure everyone followed him blindly, so he could lead an army through.

"He ordered me to slaughter any monster that didn't follow him, but I couldn't. I faked my death and started a rebellion against him. Papyrus was the second to join the rebellion, when he was ordered to do what I was, but he stayed as a mole in the inner circle." She growled, but not at either of the skeletons. "I've told him to get out of there, that it's too dangerous now, but he refuses."

"Undyne you know why I stay." Papyrus wasn't happy.

"Yeah and I think it's dumb…"

"Undyne…" Papyrus growled at her in a very not papyrus-like way. She shied away from his tone.

"What are we going to do?" The human hadn't said anything during the talk, so their question caused everyone to jump a little.

"We have to face me… Sans… but we can't go in alone." Papyrus and Undyne exchanged a look and shook their heads.

"Not possible. There's no one in the Underground left to rebel. They've all conformed… or turned to dust."

"What about Alphys? She was always for the greater good." Undyne stood with a violent jerk and walked to the sink. She wiped down the counter and wrung the towel in her hands.

"Alphys… She's not going to help us." Sans was confused.

"Why not? Was she dusted?" The thought sent a pang through his chest. Undyne shook her head sadly. She turned around and pulled off her eye patch. Where her shining black eye should have been was a mass of scar tissue. The hole was ragged and painful looking, despite it being and obviously old wound.

"If only she was dusted… no. She was Sans' number one supporter, but she never told me. I went to her when I was going to fake my death, thinking she would help me. Boy was I wrong." Undyne grimaced and replaced her eye patch. "She attacked me, yelling at me for abandoning the new age of monster kind. She cursed me for abandoning her. She ripped my eye out, and I just barely escaped. The reason Sans accepted the story of my death so easily was because Alphys presented my eye as proof… That traitor…"

Sans clenched his fist on the table and let out a low groan. How was he going to fix this?

"There is one person who might help us…" Papyrus wasn't sitting. He had been standing by the window the whole time, watching out for anyone who might be coming up the way. Everyone turned to him with hopeful eyes, except for one.

"Papyrus no. There's no way he'll-"

"We have to pay a visit to Mettaton."

I adore every single AU Undertale has to offer, and I was reading a story by FlightyFelon and just adored their Underfell headcannon. I just had to write something myself.

I know I'm in the middle of another Undertale story, but I'm not abandoning it! Love Yourself will continue, but I just needed a change of scenery.

Thank you everyone for reading! I hope you enjoyed it, and I hope to have the second chapter up before the end of the week!

Until next time!
~Starlight