Disclaimer: I do not own Undertale. The game is the property of Toby Fox. If my OC is similar to any trademarked character and/or OC from another fanfic, it is purely coincidence.

A/N: This is my very first fanfic I am making, so please excuse my grammatical mistakes. I do hope you enjoy the experience.

'Thinking'

"Speech"

"Empowered Speech" (Used when casting magic)

Preview

In a room was a man that had seemingly gone insane. Why you ask, well he was currently occupying himself with repeatedly punching a big door while crying out "Not again!" and "Why me!"

You see, he has a curse that was once thought to be a blessing. The ability to 'RESET' the timeline and load specific parts of the timeline, which he referred to as 'SAVE's. Using this ability, he quickly made friends with all the monsters, and would keep a promise that he wishes that he never made. Problem is he does not have the SAVE file to go back and prevent himself from ever making that promise.

After calming down from his little outbreak, the man slumped down to the ground. His eyes where empty as he bitterly reminisced about what brought him to this point, about that damn promise he made to a friend.

Flashback

Standing in front of the door which would lead to freedom, was a man about average height. He was wearing a black leather biker jacket with soft blue shirt underneath, black pants with a leather belt, which had a silver buckle, and black steel toe boots. He had black hair, brown eyes, and an oval face with a short, neatly trimmed beard. The odd thing about his beard though, is that it has two red streaks that line his jaw, nearly coming together under his chin.

Standing not too far from him was a short skeleton, who wore an everlasting grin. He was in his trademark clothing, a blue hoodie, white shirt, black shorts and blue slippers. His name, Sans.

"Well kid, are you gonna break that barrier?" Sans asked.

"Yeah yeah, I'm just thinking."

"About?"

"Well, you remember that I told you about how dangerous it would be if another war broke out between monsters and humans?"

"Yes, you specifically told me about the military and their weapons, the fact that they outnumber us, and that they could even hunt us no matter where we are. Listen kiddo, I know that you worry about us, we are your friends and that you think that the other humans will reject us, but have a little faith would ya."

"Sorry Sans, it's not what I meant. What I meant was what if they experiment on you, or use you as sub-human labor or worse. If that happened I would never forgive my…" He was cut off by Sans letting out a small chuckle.

"You seem to take well after your MOMster, you worry way too much."

The man just stares at Sans with a flat look. Shaking his head he approaches the barrier, which can only be broken at the door for some reason, and places his hand on it. He starts to concentrate as hard as he can, and he feels something pull at the back of his mind. Next thing he knows he is a white room with a person standing in front of him. This new person waved a staff and a pulse was sent out. The pulse returned and the person nodded. Casting his gaze at the one that summoned him, he simply said "The barrier will not break, not until every monster that is in this cave has been killed." With that said he disappeared and the room went black.

"KID! KID! ARE YOU OK! COME ON, DO SOMETHING AT LEAST!" The man wakes up to Sans that was shaking him and screaming at him.

"Sans? How long was I out?"

"About five minutes. What happened? Why is the barrier still up? And what was that pulse?"

The last question really caught the man by surprise, if what that vision said was true, would he have to kill all his friends and family to break the barrier?

"Sans"

"Yes?"

"I got a vision, and it was a bad one. I know how to break the barrier, but to do so… it will not be worth it and will take a lot of time."

He looked and Sans and immediately regretted saying that. Sans was furious.

"Not worth it? NOT WORTH IT?! Is it not worth freeing the monsters? Is it not worth our hopes and dreams? HOW COULD YOU SAY THAT?!"

"Sans Listen to…"

"NO YOU LISTEN! What are you thinking? Promise me! If there is a way to break the barrier then you will."

"S-Sa-ans"

"Please, Tristan I beg you."

"Sans I, I don't know what to say." The newly identified Tristan said.

"Just say yes."

"Are you sure?"

"Yes"

"Fine I will."

Flashback End

Tristan just sat there, wallowing in sadness. 'How long ago was that? 812 or 813 RESETs ago? I can barely remember it now'. He had done a lot of research, because if he was gonna break the barrier. Then he would find a way to bring his friends back. He found out that with a special bit of magic, he could save their souls inside of him. He even found out how to recreate their bodies and put their souls back into the bodies. But, and there is always a but, he has to kill All the monsters, and that is where a wildcard appears. You see, a specific monster that goes by the name of WD Gaster that only appears on rare occasions, when certain conditions occur, and only after all the monsters are dead.

The conditions are as follows: 1, In a previous 'run through' as he calls it, he must be a pacifist. 2, He must kill everyone (1). And 3, He must enter Gaster's Laboratory, which Dr. Alphys did a great job of making it very difficult to enter.

'It hurts so much to have to do this. I made that promise, I will keep it, but seeing their faces so happy, and then killing them in the next run. I don't know anymore, how many times I had to do that. O yeah, 406 to 407 times. The genocides though, seeing the hate in Sans' eyes. How I have to decline his begging to reset and bring his brother and friends back. Toriel's look of pain, and betrayal when she realizes that I am going to kill her. Papyrus saying that he still believes in me. Undyne that wants revenge for killing her friends. Alphys, her reaction, her words. Mettaton believing she can still be fixed. Napstablook, Asgore, all of them.'

He had just completed his pacifist run and broke down in the one place he knows is private. Well after he alludes Sans that is. 'Speak of the devil' he though as Sans walked in. Curious the skeleton wandered over to his friend when he saw the condition Tristan was in.

"What's wrong kid? Looks like someone killed your puppy or something?"

"Sans, do you think I'm a good person?"

"Where is that coming from? Well yeah I do think so. Are you ok?"

"Yes just thinking" 'though you probably don't know what I'm talking about' he added in his mind.

"Are you sure? Cat got your tongue? 'Cause I think now is a PURRfect time to talk with someone."

"You and your puns, listen I can't break the barrier. Something is blocking me from doing so." He smoothly lied. It was easier to lie now seeing as he would RESET soon anyways.

"Are you sure?"

"Well you did ask why I was feeling down."

"True, but if you though being a better person would change the way the barrier works, then you would have to become a saint." Sans gave him a piece of paper.

Tristan looked at the paper and chuckled. The paper was cut to ribbons at the end with the words 'TAKE ONE FOR A TEARABLE PUN' written on it.

"Who else would laugh at my puns, well except Toriel?"

"Touché."

"Well I'm heading to Grillby's, want to come with? I know a shortcut."

"Thanks but no thanks Sans, I'm a bit tired, so I'll head home for now."

After saying their goodbyes, the two split up. One heading to Grillby's, the other about to press RESET, and start his personal hell once again.

END

A/N: Don't worry Frisk and Chara both exist. All will be explained in future chapters.

I hope you enjoyed the read. As said before this is my first fanfic, so please go easy on me with the criticism. If you have any ideas you would like to share PM me and I will see about adding them to the story. Also if you have any Sans puns could you PM me some, I am not very creative with puns.