Hey guys! Whoa, it's been almost a year since I've written any fanfiction. I've been battling depression, and didn't feel the spark I needed to write. But thanks to my discovery of Undertale about two months ago, I'm feeling that spark ignite once more.

I do have an OC in this story. She is on the cover I crappily drew. I know opinions of OCs aren't usually that great, since a lot have been self inserts and Mary Sues. I don't blame people for disliking OCs. But I would like to take a second to share with you how important this particular OC is to me.

If you want to read about Polari, go on over to my profile. I really recommend it. With some background, you'll understand why she is the way she is in my story, and how important she was to me growing up.

Thank you for reading my rambling! This is the only long author's note I'll make!

Enjoy the chapter!

Story Title: Freak of Nature

Rating: T

Trigger Warnings: Mentions of rape

Frisk will not be gender specific in this story. I will be using 'they' pronouns.

Disclaimer: I do not own Undertale. Credit goes to Toby Fox.

Summary: A mysterious monster enters Mt Ebott from the Surface with three tasks: save a human child, avenge the deaths of six children by killing King Asgore and... kill the one responsible for the resets?! Sans has to figure out who this monster really is, who she's working for, and exactly how much she knows about time traveling.

FINAL SPOILER WARNING: This story heavily spoils the Pacifist run and Sans' knowledge.

Chapter 1

~.~.~

Flowey scowled as he watched Frisk and Toriel go into the Ruins for the umpteenth time.

"This is ridiculous!" Flowey fumed. "How many times has that brat done this? How many times have they saved everyone? Why do they keep coming back? They just wanna see me suffer…"

A loud thud drew Flowey's attention from the entrance to the Ruins. His petals stiffened.

What was that? Hasn't happened before…

He could sense another presence entering the underground, with a soul. In the darkness, Flowey heard soft footsteps. He squinted his eyes.

This is something new. Is it another human? He sneered to himself. This'll be fun! Only this time, I'll kill it without interference!

Flowey grinned evilly, his lust for blood exciting him.

Suddenly, a pair of molten eyes was staring back at the flower, cold and lifeless. Flowey quickly morphed his expression back to a pleasant one, smiling brightly at the visitor.

"Howdy! I'm FLOWEY! FLOWEY the FLOWER!" He introduced in a saccharine tone. "Hmmm… You're new to the underground, aren'tcha? Golly, you must be so confused! Someone ought to… teach… you…"

Flowey stopped his speech when the stranger stepped forward. It wasn't a human at all! It was a white fox monster. She was short, about five feet tall, and small in stature. She was wearing strange clothing: a black shirt with no sleeves, red jeans, black leather fingerless gloves, sand flat black shoes. There were two earring on her right ear, one black and the other red. She had a weird black crescent moon mark on her muzzle. But that wasn't the strangest part. The monster's blood red eyes were boring holes into the flower, as if she was restraining herself to not kill him.

"No way… you're a monster… how did you…?" Flowey stammered, staring up at the fox monster. "Who are you?!" Something was way off. What the hell is going on?!

The monster took another step towards Flowey threateningly.

"Are you braindead? Answer me!" Flowey shouted, his face changing into a scary grin.

Another step was taken. She was standing right in front of Flowey, arms crossed.

"…" Flowey was speechless. There was something really off.

The monster lifted a gloved hand in the air, a red aura emitting from her palm.

That's when Flowey knew he was in trouble. She wasn't just any normal monster. She was a little killing machine, not so different from himself. He could see it in her eyes. And he could sense it in her soul.

Flowey quickly disappeared in the ground, frightened for the first time in his soulless life.

The monster lowered her hand, sighing. She pressed a tiny button on the black earring.

"Audio diary day one." She spoke. "I'm about to enter the Ruins in the underground. No signs of the child here. There was, however, a little flower that thought it could trick me. He showed his true colors soon enough. They were right. No monster, no matter how big or small, can be trusted."

Polari glanced a golden glimmer. She stopped to stare at, but didn't interest her enough to go near it.

After pushing the button again to end the recording, Polari entered the ruins, ready to destroy any monster that got in her way.

Toriel sighed in defeat as Frisk left the Ruins. She bit her lip as she trudged back to her house.

Why does this pain feel so familiar to me? She wondered sadly. There have been six other children, but for some reason, this feels different…

Toriel's phone buzzed. She had received a text notification that the puzzles have been activated again.

"That's odd." Toriel murmured. "Is it… another child? I must go investigate."

~.~.~

"You've got to be kidding me." Polari seethed after she fell through a hole for the seventh time. "What kind of place is this? Only dumb monsters would put up a sign that says 'don't step on the leaves,' have me walk on them anyway, and have a sign chastise me for it."

Polari was not expecting to be facing off with puzzles. She was expecting diabolical monsters to be coming after her. Instead, she was trying to figure out a maze. How anticlimactic.

So far, Polari had come across signs that were obviously meant for a child, arrows pointing to the obvious switch for a puzzle, a dummy, little frog monsters that weren't even worth killing, a bridge of spikes (she decided that wading through the water around the spikes was much simpler), and now this.

She walked back up to the puzzle, remembering which way was not the right way, and made it across. She then spotted another Froggit. Not in the mood for more messing around, Polari snatched up the Froggit.

"Tell me how to leaves these ruins." She snapped, fresh out of patience.

The Froggit stared at her in defiance, already hearing from other Froggits and Whimsums that this new monster was trouble.

Polari glared at the frog. "Tell me, now."

The Froggit's eyes remained unchanged, fearless.

"Ribbit, ribbit. (She... Toriel, will stop you.)"

Suddenly, a jolt of pain went through Polari's mind, as a memory tried to resurface.

You won't get away with this! My family will stop you!

"No… I won't let it…!" Polari clenched her teeth and hands, choking the Froggit. A burst of Polari's monster magic incinerated the Froggit instantly, leaving behind only dust.

Calming down, Polari wiped the dust on her pant leg, not bothered by the death. Other monsters in the area that witnessed the horrific act fled, making a point to warn others along the way.

I was hoping the first casualty would be a monster more… formidable, but whatever. All of the monsters down here are evil. Even if they didn't take part directly, they all acknowledged the murder of six children, and did nothing.

Polari walked forward, shoving her hands in her pockets. I must remember my mission and nothing else. When I mind this missing child, whatever their name is, I will bring them back home to the Surface. I will avenge the deaths of the six children and kill the monster king, Asgore. And when I find the one responsible for causing time to alter, I will kill it. These monsters will not succeed in their plan to take over the Surface!

~.~.~

Just as Toriel was about to investigate the mysterious puzzle activations, she was shocked to find Moldsmals, Whimsums, and Froggits approaching her house.

"What is the matter?" Toriel blinked.

"Ribbit, ribbit! (There's a fox monster that killed one of us!)"

"Rumor has it that she came from the portal outside Mt Ebott." A Whimsum added meekly.

"A monster from the Surface?" Toriel frowned. "Oh dear. Everyone, go and hide! I will deal with this myself."

Without looking back, Toriel rushed ahead.

Could this be a traitor? Or… the traitor that helped seal all of monsterkind underground?!

Toriel stopped when she spotted a white furred monster walking towards her.

That must be her…

"Please stop right where you are." Toriel commanded firmly.

Polari stopped, smirking. "You must be Toriel. You're just some goat. Oh, this is just precious. Are all the monsters down here frail and weak? From what they were telling me before I came here, they made you all out to be potent."

"They?" Toriel repeated, her frown deepening. "Who sent you here?"

"Sorry, that's classified." The short monster snickered. "Now, if you tell me where the human is, I may spare your life."

Polari was lying. There was no doubt the human couldn't have gotten through the Ruins without coming across Toriel, thus helping send them to their execution. So, Polari will deliver the same fate.

Toriel gasped. She's after the child! I must destroy the exit to the Ruins!

While Polari somewhat had her guard down, Toriel shot a fireball in her face, temporarily blinding her.

"Aaugh!" Polari cried, covering her face with her hands.

Toriel ran back to her home as fast as she could. All she could think about was Frisk's safety. After running down the stairs and through the long hallway, she finally came to the exit. She aimed her fireballs at the door. However, something knocked the wind out of her, almost depleting her HP. Toriel laid on the ground, coughing.

"You know, you're not very good at running." Polari towered over the goat monster. "Hell, those little frog monsters ran faster than you. You see, I may be smaller than you, but I more than make up for it in skill. I honestly could have killed you just now, but I need some information from you."

Toriel gritted her teeth, the wound on her back getting more painful each second.

"I'm not telling you a thing." Toriel said as calmly as she could. "You will not hurt my child."

"Your child?" Polari almost choked. "That's a funny joke."

Polari put her hand against the exit door, feeling the coldness of the outside.

"Maybe I should skin you so I can have a fur coat to continue my mission." Polari mulled.

Toriel only grunted.

"Sorry, I've been told that I have a sick sense of humor." Polari shrugged.

"Please… don't hurt anyone out there." Toriel begged, knowing this was probably the end for her. "Because if you do… Asgore will destroy you."

Polari scoffed. "It's too late for mercy. Asbore is no threat to me."

Before Toriel could say anything else, Polari shot an aura orb at Toriel. Without looking back, Polari exited the ruins, only to find a green patch with nothing there.

"Weird." Polari moved on, passing the final door.

Flowey was watching from behind, intrigued with Polari's choices.

"She killed a Froggit out of sheer frustration about something, but killed Toriel out of malice." He grinned sadistically. "Interesting. With the right kind of influence, she could help me destroy this world. I'll be able to kill the human as well. Hee hee hee!"

Flowey disappeared below ground.

Sans was asleep as his post in Snowdin. After helping Papyrus with his "puzzles," he went back so the human could "fight" Papyrus.

what is this kid lookin' for? Sans thought in his subconscious. they have reset so many times now. should i reveal to them that i know about the save files, loading, and resets? maybe then i'll get an understanding.

Sans could sense someone walking past, but was too lazy to open his eyes. It was then that he remembered that usually around this time, he goes over to the exit doors of the Ruins to chat with his lady friend Toriel. He has met her so many times before Frisk reset, but he refused to let Toriel know.

Sans stood up and stretched, his bones cracking. He saw no sign of the person that walked by. Shrugging, he headed to the doors and knocked.

"hey tori! you there? i came up with some new material." He announced proudly.

But nobody came.

"tori…?" Sans was surprised. In every timeline, Toriel was always there at the exact time. What's different now?

Suddenly, he could hear some shuffling and groans.

"tori!" Sans banged on the door. "what's goin' on in there? you okay?"

"You…" Toriel wheezed, hanging on to one HP. "You've got to… protect this human child… please…"

"what…?" Sans was confused. This has never happened.

"There's a fox monster…from the Surface… after the child, named Frisk. She almost killed me… trying to get information… about their whereabouts." Toriel coughed hard.

San couldn't believe his nonexistent ears. There's an anomaly in this timeline?

"tori, i promised you that i'd protect humans that came through here. frisk won't be any different." Sans assured Toriel. "but what about you? you don't sound too good."

"I'll be fine." Toriel replied, not sounding very convincing. "I'm hanging on to my life for as long as I can. If I can make it back to my house, I'll eat to restore my HP. Please… go!"

Upset, Sans did as he was told and ran, hoping this fox monster doesn't hurt anyone else.

why in this timeline is there some random fox monster after frisk? from the surface, no less? i just hope papyrus hasn't confronted this fiend yet!

If you read my explanation for Polari, you know why she's such a dick. XD like I said, she's loyal to the cause and sarcastic. And since she believes that monsters are in the wrong, she's cruel and extremely sarcastic towards them.

I apologize if this chapter was boring. I suck at intro chapters. But hey, more action will be coming next week, as Sans and Papyrus get in on this adventure.

If you want, please leave a review! Some feedback would be nice, since I haven't written much of anything in a while.

Thanks!

PRK