Disclaimer: I don't own Undertale

.

Frisk had a voice in their head.

They'd had a voice in their head for a very long time now. It had started with little things, things they were okay with, or wanted to do anyways. Things that sounded like a good idea. But then it told them to do other things.

Things they didn't want to do. Things they were scared of.

The first time they decided not to listen to the voice, there was a weird pause at the back of their mind. They held their breath, even though they didn't know why they were suddenly anxious.

Then their limbs moved on their own.

They got up and did what the voice told them to do.

When Frisk got control of themselves again, they were terrified. They ran off and cried, hiding and hoping no one could find them. But after they calmed down, the voice told them to go back.

They gripped their hands to their head, too scared to move, begging the voice to go away.

They lost control of themselves again.

It wasn't long before they stopped trying to fight it. When the voice was quiet, they could do whatever they wanted. When the voice told them to do something, they just did it rather than lose themselves. They didn't have a choice.

They were just a puppet.

.

One day the voice told them to walk up the cursed mountain. Frisk wandered around, taking the time to play in the woods.

They always took the chance to make their own decisions.

Eventually, they found a cave with a huge chasm. Looking down, they couldn't see the bottom.

The voice told them to jump.

.

Frisk froze, just as scared as they had been so long ago. The voice had forced them into terrifying places, but it had always told them to stay alive, keep going.

Now it wanted them to die.

They gritted their teeth and turned away, praying that just this once, they could disobey. They tried, even though they knew how pointless their struggle was.

Their body lost its tension, disconnected in a terrifyingly familiar way. They turned back to the chasm, walking slowly, so very, very, slowly. Their heart was pounding wildly in their chest, the involuntary reaction the only sign of their fear. Their face was blank as they took a step, then another, then another that landed on nothing but air.

The voice wouldn't even allow them to scream.

.

Frisk jerked awake, body aching as they scrambled around in the patch of yellow flowers.

Alive.

Somehow, amazingly, they were alive.

They cheered and laughed in a way that was at least halfway hysterical, before hearing the voice sobered them. They quickly picked up the stick as ordered.

Looking up, there was no way they could get out that way. The only other way out of the cavern they were in was a tunnel. A hallway, they realized, with pillars and bricks.

They walked down it and through a doorway, finding a smiling flower. The flower, apparently named Flowey, explains some things. Things that don't seem to add up. They were about to say something, when the voice tells them not to do anything. They let the 'friendliness pellets' hit, they stay still even as they're surrounded.

They're saved by a goat monster named Toriel.

Frisk follows her like she asks, going through puzzles in the ruins. They look at a few things, and freeze when they hear a new voice. This one is softer, and seems content with simply commenting on things they see rather than controlling them. It says it's name is Chara. The first voice is blessedly silent until Toriel asks them to talk to the training dummy. The voice tells them to do so.

Things go fine, and Toriel is nice. They like it here.

Frisk ends up stumbling into a fight.

The new voice says the monster is called a froggit. The first voice tells them to compliment it.

They do as it says.

It's all they can do.

.

Underground, surrounded by monsters, and stuck with a new voice, Frisk begins to fall into a routine. They wander, Chara reading or cracking a joke at whatever they point out, and the voice directing them in battles. Occasionally, it would tell them to do something, like put on an old ribbon or carry a toy knife they found, but for the most part, it seemed to only want to give orders in a fight at the moment.

Toriel cared for them, taking them in and giving them things; more of a mother than they'd ever had. They were happy for a few days, until the voice reappeared while Toriel was teaching them about snails.

It told them to ask how to leave.

.

Frisk stood outside the closed Ruins doors, silently mourning the loss of something that had felt like happiness.

They hadn't wanted to leave Toriel. Even as she hugged them, crying and telling them to never return, they'd wanted to cling to her and say they'd stay.

But they didn't. The voice told them to leave.

Chara noticed a camera poking out of a bush, so they started walking down the snowy path. They walked past a fallen branch, only to turn back when it is broken with a loud crack. Chara seemed nervous, and Frisk was too. They shivered as they walked quickly down the path, certain they were being followed.

The voice told them to stop. They shifted anxiously from foot to foot. They could easily walk through the large arching gateway over the bridge, get through and away from whoever was following. They really, really wanted to.

Especially when a deep voice told them to turn around.

.

Frisk beamed up at Toriel, telling her they'd stay with her almost simultaneously as the voice ordered that same thing. They hugged, Chara quietly muttering that they finally kept their promise.

Frisk was so happy, they almost didn't notice it. In the whirlwind of Toriel adopting them, their duties as an ambassador, and all the monsters moving up to the surface, the voice had gone silent.

Chara was still there, a comforting presence snarking in the back of their mind, but the voice hadn't said a single word. They reveled in it, being able to make their own decisions. As time passed, they began to think that they were finally free of it.

Almost a year after the barrier was broken, they bolted awake in the dead of night. They shook their head, trying to figure out what had woken them up. Toriel had left a slice of their favorite butterscotch-cinnamon pie in their room, but that wasn't too uncommon. They vaguely felt Chara yawning, and then heard something else.

The voice was back.

It told them to reset.

They fought with all they had, but they just lost control.

Pointless, as always.

But this wasn't just fear for themselves, this was fear for everyone. Everyone would lose everything. They struggled and screamed at the voice, but were unable to do anything but watch as the timeline unraveled around them.

.

Chara was upset with Frisk. They were upset with everything. They knew about the voice, but still cried out asking why, why had they gone back? What was so wrong with the life they had had that they had to start over?

Frisk was silently asking the same questions.

The voice said to dodge Flowey's bullets this time. Said to fight the training dummy.

Said to kill the froggit.

They tried not to, and control was taken from them. Chara just kept asking why.

The only thing that kept Frisk from collapsing next to the poor froggit's dust was the knowledge that Toriel was standing around the corner, waiting for them.

They had to keep going.

.

Something was wrong with Chara.

The voice kept telling Frisk to fight, to kill, to hunt down every monster they could find. Chara had cried, had raged, had begged, but the voice kept telling them to kill. They tried not to, pointless as it was. They fought and deliberately missed, but they could only get away with that a few times before they lost control and were forced to kill again.

EXP thrummed in their veins, LV floated in their mind like a cloud.

Chara was quieter, and the things they did say were darker, more twisted, until finally they started counting down how many monsters were left still alive in the ruins.

Frisk remembered that Chara saw all of monsterkind as their family. They wondered if Chara was going insane.

They wondered if they were too.

.

Toriel fell in a single blow. Helplessly, Frisk watched their body trudge through her dust and leave the empty ruins without even looking back.

They found Flowey at the end. He just kept smiling, calling them Chara and cheering about how much fun it would be to kill everyone together.

.

Frisk's knees gave out as they regained control of themselves, eyes aching with tears that wouldn't come.

It was too much, it was all too much.

They had killed Toriel.

They had killed Papyrus.

They had killed Undyne twice, as she miraculously held her dust together and survived.

They could hear Chara, twisted and dark, scoffing at them for being a crybaby. The only sad thing about this is that she's not a challenge anymore, they said.

The voice told them to get up, to keep going.

For once, Frisk willingly let it take away their control.

.

Chara was seething as Flowey ran away. He was scared of them.

Even Flowey was scared of the killer they had become.

Frisk walked into the golden hallway, hoping that Asgore would be able to kill them for good. It was the only way to stop the voice. It would never work, though. Not with their determination.

Despair ran through them when Sans stepped out from behind a pillar.

Not Sans too, Frisk wanted to cry. Not Sans, who had never fought them before. Not Sans, who only had one HP.

Why hadn't he evacuated with everyone?

They were going to kill him.

.

Or maybe, they wouldn't.

Chara raved as they returned to the save point. Finally, a challenge, a real challenge.

They died over, and over, and over, falling to Sans' incredible power. They only watched, their body either moving by the voice's control, or Chara's.

And then, Sans spared them.

Frisk accepted as fast as they could, before Chara could strike out or the voice could say no.

As they returned to the save point, Chara chided them for falling for such an obvious trap. We killed his precious brother, they said, he would never forgive you for that.

They agreed, a dirty brother killer like them didn't deserve mercy.

.

Sans was dead.

In the end it was Chara that killed him, striking out as he dodged their attack. He had stumbled out of the hall, dust and ketchup trailing behind him.

Frisk stood, frozen, as that final, twentieth LV surged through them.

Chara was cackling.

They had a hard time trying to figure out why they shouldn't join them.

The voice ordered them to keep going, so they shook themselves off and left the hall behind.

.

Frisk stared as Chara ripped themselves out and took form in front of them.

As Chara offered them a choice.

The voice silent, Frisk cried out that no, they didn't want this, they wanted the world to live on.

All they had ever wanted was to live.

Chara seemed confused. Then they smiled.

Since when were you the one in control.

Frisk gasped as Chara lunged forward, laughing as they thrust the true knife into them. They felt the damage hit, spreading to hit the whole world.

And it all fell to nothingness.

.

Frisk didn't know how long they floated in an infinite void.

They couldn't feel anything.

Silence, true silence for the first time that they could remember, filled their head.

They were alone.

They just wanted to reset it all.

Interesting, Chara said, you want to go back. Back to the world you destroyed.

The voice did that, Frisk wanted to say, but didn't. The dust was on their hands, in control or not.

But still, they said yes, all they wanted was to be with their family again.

Then Chara offered a trade, the world for their soul.

The voice was silent here, Frisk could make their own decisions.

They agreed.

.

Frisk blinked awake in the bed of golden flowers, back at the beginning. They could feel their soul still in them, but slightly disconnected, like it didn't fit quite right.

Like it wasn't theirs anymore.

Still, they were glad. The world was back, everyone was back, they were back and no longer tainted with EXP and LV.

They were especially happy about that. The lack of feeling, not really sure why it had been bad to hurt others besides because it was what the voice wanted, was horrible to remember.

That must be how Flowey feels, they thought.

They tried not to think about it.

After a while, Frisk realized that they'd been lying there for some time. Neither the voice nor Chara had said anything.

They got up and moved forward.

.

Chara was still there, Frisk realized, though they were achingly quiet in the back of their mind. It wasn't until Toriel left them alone in the long hallway that they finally spoke.

Frisk, Chara whispered, horrified, what did I do?

I killed them. I killed everyone.

Frisk tried to say it wasn't their fault, but Chara kept going.

I killed everyone, and I enjoyed it.

It wasn't really you, Frisk said, it was the EXP and LV, and the voice. It wasn't your fault.

I still killed them.

I know, Frisk whispered, I killed them too. But it wasn't our fault. We didn't want to do it, it was the voice.

Chara was quiet, and Frisk could feel them thinking. The voice... I can hear it a little.

It hasn't said anything yet, Frisk said.

It's angry, Chara said, you're not doing what it wants. It doesn't know why.

Frisk didn't know what to say. They weren't doing what the voice said. They didn't think that was possible.

It can't control you, Chara said slowly, because I have your soul now. It can't get a hold of you.

Good, Frisk said, I know you'll take care of it.

But I kill-

We both did, Frisk interrupted, and it wasn't really either of us. I know you're a good person. We can do good this time.

We can do better.

.

They made it through. They saved everyone. They lived on, happily, and on the surface with their family.

Almost a year after the barrier was broken, Frisk bolted awake in the dead of night. It wasn't incredibly uncommon, though they were confused as to why they were up if a nightmare about the past hadn't woken them. They glanced over and saw a slice of pie Toriel had left them as they felt Chara yawning.

Then they heard the voice.

It said to reset.

No.

Chara ripped control from them, gripping the blanket and glaring into the void. Their soul is mine now.

Frisk could feel their eyes burning red with the intensity of Chara's possession.

The voice said to reset.

Never. Chara said, both in the mind and aloud. We are Never. Ever. Going. Back.

The voice was silent.

It never said anything ever again.