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  • The War Amongst Us (W.D. Gaster X Reader)
    64.9K 3K 24

    (Y\N) is a young female spy and soldier fighting in the War of Humans and Monsters. She is fighting on the humans' side of the war until a turn of events when she becomes apprehended by the enemy. What will happen when a young monster scientist tries to change her views? Thanks to Itachei on Deviantart for letting me...

  • (Underfell sans x reader (female)) UNDERCOVER
    498K 17.4K 64

    You're a human that has fallen into Mt. Ebott on the year where all humans dress as monsters...Halloween. So how will the monsters know if you're a human or not?

    Completed  
  • Can I take you to Dinner? Mafi-fell!Sans x Reader. [COMPLETED]
    209K 6.6K 33

    "How rude, not even gonna ask for a name??" He teased. "Why are you here?" You glowered, raising the whisk. The skeleton scoffed: "Well, glad you asked sweetums! Name's Sans, Sans the skeleton." - Y/N, a ritzy waitress at Grillby's is plucked from her world of pancakes and Orange juice into the gun-slinging, smoke-bre...

    Completed  
  • The Queen's service Au!Sans' x Reader {SEQUEL}
    15K 643 11

    {Sequel to: 'Can I take you to dinner?} "Miss me, sweets?" ....... "I... I uh, know this is going to sound terrible but- do I know you?" - A century has passed since the events of Sans' passing and the crowning of (Y/N). With the trials of the afterlife ahead of him and (Y/N)'s battle against Papyrus' conciliations an...

  • (Sans x Reader) When Two Souls Meet
    952K 27.4K 28

    Sans has lived through countless timelines. He's seen the kid make friends with everyone, only to give up in the final moments. He's seen the kid killed, over and over and over again. Sometimes, he'd even done the killing himself. And no one ever remembers. Not even the kid herself. It's an exhausting cycle, one that...

    Completed  
  • When Two Fates Intertwine (Sans x Reader)
    92.8K 2.6K 13

    [THIS IS A SEQUEL TO MY OTHER FANFIC "WHEN TWO SOULS MEET!" If you haven't read it, I would highly suggest it--the story won't make much sense otherwise.] Sans has finally found someone he can trust--Frisk's sister, the eighth fallen human. After months of step-siding and awkward interactions, the two are finally a co...

    Mature
  • Characters in a Story (Sans X Reader)
    4.3K 47 22

    You are a fairly normal shut-in college student. That is until an all too familiar face brings monsters onto the surface. . . . #3 Sans X Reader (May 12th, 2023)

  • Fighting for You
    33 0 3

    Wassup. This is for my stupid friends birthday. Hope you like it Grace, I stg this sucks but you wanted to see it so here you go. This is about a bunch of different AU Sans' all fighting to become your boyfriend. Have fun f*ckers. (I don't know the artist who did the cover art's name! If you know, please comment it or...

  • The Smell of Old Books (Sans/Reader)
    258K 14.7K 38

    The old bookstore wasn't your home anymore, you finally realized. It was with them. It was with him. (Sans (Undertale)/Reader. The story takes place in second person view. Reader is not Frisk!) (art is by @Elmer_Heiji on twitter)

    Mature
  • Fallen Angel (Gaster x reader) OLD
    149K 6K 49

    OLD AND BADLY WRITTEN THE REWRITE IS POSTED ALREADY DISCLAIMER: The god figure created in this fanfic is purely fictional. He is purposefully made to be prideful and cruel and is not supposed to represent any god. I am religious myself and I did not intend to attack anyones believes with this book. An angel. Sign of...

    Completed  
  • Bone of Contention (Underswap Papyrus X Reader)
    372K 14.7K 62

    Humanity is divided over one thing---the Monsters' reappearance. Some believe that they should stay aboveground, and others think that they should be sent back to where they came from. Then, there are those like you who don't quite know what to think yet. What will happen once you become acquainted with two skeleton b...

  • Prisoner of War (W.D. Gaster X Reader)
    46.7K 1.7K 14

    You are one of the few humans with magic during a war between you and the monsters. (Pre Undertale) Instead of killed you wind up captured by the monsters where you meet a scientist and doctor W.D. Gaster. Cover... I drew it myself this time

  • FRUIT OF THE VOID (Gaster X Reader)
    17.3K 792 12

    Dark, darker, yet darker. The darkness keeps growing in your life. You don't know why, but there's someone relentlessly haunting you. He won't leave you alone, and every dream you have is a nightmare. It seems peace is currently impossible for you. What great evil could possibly want to harm you? You never felt that...

  • Gaster x Reader
    160K 4.2K 61

    Pretty self explanatory. This takes place after the Pacifist route in Undertale. Through determination, Frisk was able to bring back Chara, Asriel (Asriel is Flowey per say), and Gaster. I believe that Gaster is the father of Sans and Papyrus. I also don't believe that Chara is evil. The monsters are on the surface, a...

    Completed  
  • Darkness' Eternal Bride (Gaster x Reader)
    28.8K 1K 34

    WARNING: THIS CONTAINS HIGHLY MATURE CONTENT (BLOOD, VIOLENCE) READ AT YOUR OWN RISK Money can change a lot of things. It can even change your destiny. Plunge yourself into a life of romance, science, disappearance and misunderstanding. ________________ "When you get better, I'd like to kiss you" ... Gaster only wante...

    Completed  
  • HP (W.D. Gaster x Reader)
    57.4K 1.9K 20

    You lost your father in the war against the monsters. If it was up to you every last being that fought against man would be sent to execution. But it wasn't your choice.... unless it was? That's when you decide to visit the underground. All you needed was one excuse to rage another war against the monsters this time...

  • What We Hope For (Sans X Reader) ✨UNDER EDITING✨
    131K 4.2K 62

    Everyone has a happy ending. If you're not happy it's not the end . . . . •°•°☆°•°• Y/n (that being you) fell into the underground at the age of 13 and found refuge inside a hidden house in the snowy forest. Fast forward 10 years later still no one knew of her existence. That all...

    Completed  
  • What We Fight For [Sansxreader]
    7.6K 229 17

    [THE SEQUEL TO WHAT WE HOPE FOR] If you haven't read the first book then I recommend going there first. °°°☆°°° Picking up where we left off, the group has made it to the surface. Y/n and her friends now have to figure out their life. With y/n, there is her duty as an ambassad...

  • At the Surface (Sans X Reader)
    505K 20.5K 62

    The monsters have finally made it to the surface and have been legalized to roam the surface as they please. The first couple of months have been spent as a paradise where humans and monsters have lived in peace and happiness. But as we all know, humans tend to be afraid of what they don't understand and the appearanc...

    Completed  
  • Lockdown (Prison!Sans/Papyrus/Gaster x Reader)
    29.9K 1K 9

    You weren't THAT bad of a person. I mean, you blew up a few things, and killed a few people, but that was on accident! Course breaking out of prison about 8 times wasn't, you have to admit that. So, for all your trouble, you heard you were being sent to Ebott Penitentiary, the most high security prison in the world. ...

  • Flower you today, sweetheart? (Flowerfell Sans X Reader)
    208K 5.6K 40

    All the world, just hated kind people... they threated them as nothing and put them aside. That even happened in the underworld... They saw them as a sickness, what they don't know is that sicknesses spread... (Cover made by me :3)

    Completed  
  • Northern Downpour (Underfell Sans x Reader)
    173K 5.1K 42

    (Y/n) goes to Mt. Ebbot in search of her brother Frisk. But what she finds instead amazes her.

  • Why Him? | Underfell Sans x Reader
    199K 6.2K 35

    *WRITTEN IN 2016* "Can someone please just tell me.... Why him.....?" Confidence. That emotion has been coming to you a lot ever since you had met him... But Why him...?

    Completed  
  • Scientist - GASTER X READER
    149K 4.2K 19

    Hi guys! So this is actually my first time writing a adventure story (and xReader), so I am kind of sorry if it looks crappy!! ****** A long time ago, people were missing when they climb up Mount Ebott. They say there was magic, got lost, or even died. But when you discover the secrets of the mountain, you will get at...

    Completed  
  • Gaster x Reader- Not Your Fault
    107K 3.3K 13

    You're a human who has fallen down into the underground. There you meet a certain skeletal scientist and his sons. Will you get close to the family or will you become their enemy. Loosely based on TheBombDiggity666 Dadster comics (which you should totally check out if you haven't already) and occurs before frisk's ap...

    Completed  
  • ...
    19.2K 478 6

  • Glitched Love - W. D. Gaster x Reader
    57.6K 1.6K 31

    You, a human, have fallen down into the underground. After having exploring most of it, you have successfully made lots of friends and killed no one. While you want to go back home to your town above ground, all your friends that you had made you decided to stay, or for the moment at least. Very soon, you will end up...

    Completed   Mature
  • Light in the Dark (Gaster X Reader)
    10.1K 457 16

    He went blind in a freak accident at the lab. Now all he 'sees' is darkness. Until.. he meets you.

    Completed  
  • The Ghost Above Me (Gaster x Reader)
    47K 1.7K 33

    Even though the Underground is now empty, except for some people, you still stupidly managed to fall in the once prison for monsters. Who knew you would get away from the prison with someone following you behind your back? Who would have known an echo flower would have revealed too many things? Who would have known yo...

    Completed  
  • ~Experiment~ {Yandere Gaster X Reader}
    41.5K 1.4K 26

    None of the art used in this story belong to me!!! And neither does Gaster! __________________________________________________ You were just supposed to be another shot at making an artificial human soul. But something happens. Something 'He' didn't expect. "How Interesting..."