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A Former Royal Scientist’s Research of the Space Time Continuum by stitchthelilo
Fandoms: Undertale (Video Game)
03 Sep 2025
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A little bit of rest during her research could definitely hurt, yet her eyes began to shut anyway. The consequences to this were much more dire than Queen Alphys could’ve ever expected, and after an abnormal earthquake she finds herself stuck within the endless Multiverse.
And for some reason Sans is.. everywhere??
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Takes place right after the Alphys Neutral Ending, and a freak accident sends Queen Alphys out on a travel through the Multiverse.
Series
- Part 2 of longfics
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Desert Sanctuary Guidebook by KarmaSpidr
Fandoms: Undertale (Video Game), Undertale Yellow (Video Game)
31 Aug 2025
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Clover doesn't give up his soul because justice still needs to be delivered.
The Wild East, and later practically the entire Dunes, declares independence. They declare that any human within their borders is under their protection.
Civil War looms over the Underground.
Would you like to see what happens?
Note: This is NOT a story. This is an archive containing information about my AU, Desert Sanctuary. I might write a proper story in the future, but for now, this is where you can read about the narrative, the characters and how this massive change affects Frisk's journey.
Fanart and other fan works based on Desert Sanctuary are welcome and encouraged
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GOOPY KITTY // AMALGAMATE MAD MEW MEW AU INFO by silverstormsxx
Fandoms: Undertale (Video Game)
18 Aug 2025
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what it says on the tin.
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W. D. Gaster: the Heart, the Brain and the SOUL by WittyWind
Fandoms: Undertale (Video Game)
13 Aug 2025
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“The weight of the head of a genius is equal to its value.”
W. D. Gaster didn’t want to admit it, but he could feel it, deep inside him.
His brilliance gave a future to the Underground, a machine that could convert the heat of the Earth into energy: the CORE. The other monsters would, then, use it as electricity, and bring life to their houses and their TVs and their cars and their cell phones.
But Gaster knew more. Knew better. The CORE had so much potential, so much to offer. That kind of magic had never been used before. Gaster didn't know if he could call it “magic”, even.
He was so valuable to the Underground, but… what if that made him dangerous? What would happen if he had discovered something that shouldn’t be touched, not even by monsters or humans?
W. D. Gaster didn’t want to think about it, but he could feel it, deep inside him.
What is the value of a genius, if he’s so terrified of the weight of his own head to ever use it?
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This is my first fic! I'm so excited! I'm open to any criticism, tips, and please tell me if you see any typos. I'm very scatterbrained so things might not make sense plot wise, there's probably things I'll forget to add, but i hope anyone reading enjoys it!
2S3-A, or rather, Bunker, expected to die when Gaster dropped him off in the middle of an active Battlezone and... well, the details get fuzzy after that, but he's sure Gaster activated some sort of kill-code. Bunker just... he's so tired. things cant possibly get worse. can they?
Frisk had been tracking the movement of 2S3-A since the very moment the monsters emerged from the underground three years ago. something about him was unsettling, his whole existence wasn't right. but she never could put her finger on it. until now.
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Chara and Frisk come across the VHS room of the True Lab, and Chara prepares for the worst.
There's only one problem. Or a temporary distraction, depending on how you look at it.
Frisk doesn't know what a fucking VHS tape is.
(loosely inspired by Spirit of the Underground by GreenieGirliePop!)
Series
- Part 2 of charisk oneshots :]
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You fell chasing your little sister. Now, disguised as a monster, your gambling everything to get Frisk out alive—including trusting a lazy skeleton who sees through her lies. With Asgore’s knights closing in and the king needing one last human soul, survival demands shortcuts through glowing caves and MTT Resort glitter. But Sans’s bone-dry wit and hidden power blur the line between using him… and losing your heart underground.
Neutral Route | Slowburn Sans/Reader | Found Family | Protective Siblings | 2016 Undertale fic vibes
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Frisk enters the True Lab, and well… they certainly don’t like what they find.
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How Do You Kill a Time Traveler by ZJFoster (toxicnuts69)
Fandoms: Undertale (Video Game)
15 Jun 2025
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let me describe to you a hypothetical situation. you are a time traveler. you work in the business of space and time and whatever distortion that may be caused by any such anomaly. timelines jumping left and right and the space-time continuum would be bursting at the seams if this loop wasn’t trapped in its own bubble, making your job of discerning who being positioned where in time in space irrelevant and admittedly— a lot easier. your job is to do whatever it takes and whatever you can to shut this down, even at the risk of your own life. you just wish he wasn’t here with you. even though he needed to be. couldn’t he have taken the day off? you can’t help but wonder how many times you’ve stepped out that door.
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After everything went to black, Clover asked themselfs if this was how death was. If they had anyone to wonder.
It was too dark to see, too silent to hear, too empty to even think about it. A little more and they could feel the cold, hard glass of the container they're inside, trapped for who knows how long. It could be hours, it could be days, or it could be centuries.
It feels like centuries, until it doesn't.
And a dark, misterious ceiling with a light too bright welcomes them. It's not a warm welcome.
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What if everything you knew and loved crumbled around you, and all you could do was sit and watch? What would you do if your friends all died, and the most you could do was watch on a big screen?
These memories were no blessing, not at all. Even if she could warn them, she had to die over and over and over and over and-
It just.. wasn’t worth it, it never would be, not to Alphys.
OR
Alphys begins to remember resets, and she wished she didn’t. Oh how she wished she didn’t.
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As the Royal Scientist of the Underground, Doctor Gaster was used to being given various tasks by the king of the monsters, Asgore. The first of them since they had all been sealed underground after the war was to help monsters settle down into their new home. And the second of them had been to establish a more consistent power source for monster-kind. Of course, the Steamworks had originally been developed to do the same thing, but the power it provided wasn’t nearly enough to cover all of it.
Over the course of several years, the Royal Scientist had designed the CORE and had it built, a much larger version of the Steamworks that managed to successfully run power through the entire underground. And it wasn’t even like his position had only been granted to him after being sealed underground, he’d been working for the king and queen for what must’ve been at least a century. Pros of being a monster who’s yet to have children, he supposed.
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A short story about W.D. Gaster prior to falling into his creation.
Series
- Part 1 of Undertale/Deltarune Fanfics
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[ It's around seven years since the sixth human fell into the underground. With six human souls captured but no luck in obtaining a seventh, the monsters in the lab decide to start on a new project. ]
OPERATION NEW SOUL
The plan to create a human soul.What if they combined a monster soul with a human one. It seemed silly really, but what could they say, no? So they tried it, They gather fragments of the previous human souls and infuse them with determination.
With half of a monster soul, and half of a human soul—they made…well, a soul. A stable one, maybe? No one really knew.
Some urge immediate use, fearing it will wither like the others. But the lead scientist insisted, “We must wait until its determination is strong enough to break the barrier.”
It seemed foolish. How could a soul, cobbled together in a lab, be strong enough?
Until you’ve opened your eyes.
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(DISCLAIMER: ALL OF THIS TAKES PLACE AFTER A TRUE RESET)
(DISCLAIMER: I HAVE NO EXPERIENCE WITH PSYCHEDELICS. I DO NOT KNOW HOW PEOPLE ACT WHEN HIGH. FORGIVE ME FOR THIS.Frisk should NOT have eaten so many magic mushroom-laced brownies, especially after just falling down a mountain into an underground world of monsters...
Now, a very high, slightly chubby child must find their way through this world, making friends--and losing clothes--along the way...
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Gaster had lost count of the days since he first entered the Void, but since that day, he had watched and analyzed each and every timeline there was. Just a few more resets, he calculated, and the timelines would start to mix. He had to make things right, stop the resets, and to do that he had to leave the Void.
UPDATE 2024: NEW EPILOGUE!
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Does That Mean That There Are Dogs Inside? by OhSunnyKnight
Fandoms: Undertale (Video Game)
21 Dec 2024
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How Sans and Alphys met
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Morality by Huh_What_Nani
Fandoms: Undertale Yellow (Video Game), Undertale (Video Game), Undertale Yellow
12 Nov 2024
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You were happy to just spend time in the Wild East, something was almost always going on. The sheriff and his posse kept things interesting.
You didn’t anticipate that being forced into a new job would coincide with a budding relationship with your favorite sheriff, but you weren’t about to complain. So what if you had to keep a couple of secrets about your job?
Everything was fine until your job made you begin questioning your morality.
Series
- Part 1 of Mortality
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Mortality - Lab Entries by Huh_What_Nani
Fandoms: Undertale (Video Game), Undertale Yellow (Video Game), Undertale Yellow
04 Nov 2024
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Summary
Lab entries for the events of Mortality
Series
- Part 2 of Mortality
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Summary
A particle physicist working in Ebott City is pulled into a project tasked with unravelling centuries of research to bridge the gap between human and monster science. As she delves deeper, she becomes entangled with an enigmatic entity that hides the desired explanations from her.
Driven by an insatiable need for answers, she fixates on one goal: to rip this 'man who speaks in hands' from the abyss, no matter the cost.
(Sorry!! I’m bad at writing summaries)
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It's been 6 years after monsters surfaced they have taken over everything. Humans have been hunted down to nothing due to the monsters outcry for revenge. A college girl gets captured and is sold to a skeleton monster to now solve the lack of humans to hunt. Will Seven be able to break free from the monsters of her world and get shown some safety in the next world.