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English
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Published:
2026-04-05
Updated:
2026-04-05
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1,185
Chapters:
2/?
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10

Underside - an Undertale AU

Summary:

Universes, infinite possibilities.
So what was this one called?
Underside.
A universe with unique properties and an infinite story.
A long time ago, there was a war between two races.
Monsters and humans.
On day, the humans sealed the monsters underground with a barrier that could only be broken by seven human souls, or a monster and a human.
That is the story that many have been told.
Yet one human falls into the Underground, one who's SOUL does not possess the magic inside of her.
But she can earn her trait, if she can escape the Underground.

This AU is mine! DO NOT REPOST OR STEAL!
Undertale is owned/created by Toby Fox!

Chapter 1: Before we start....

Chapter Text

Underside - an Undertale AU

Before we start...

Hello! I'm Harmony, I'm using my friend's account to write this. Shout out to her! This is my first time with making an Undertale AU, and I have this puplished on my Wattpad account as well (https://www.wattpad.com/user/Harmonydafox) I don't think many people will read this or know it's existance, but I'll write it anyway! This is still in the works and I'm still coming up with lore. Underside is my 90's/2000's base AU, which was inspired by Love, Death, and Roller Skates on Ao3 by Spadillelicious! Some things to know is that in this au, Frisk and Chara are cannonicly girls. I also make Sans and Papyrus female-ish, not sexually or in a weird way. They are very unique with their personalities being different from many AUs. Please nobody post my work, this is mine! ALL ORIGINAL IDEA FROM MY AUSTISTIC MIND!!! Undertale is owned and created by Toby Fox.
I'm still trying to write the plot, so you'll see what happens.

If anyone wants to help me with this AU or to request anything, let me know in the comments or by email; [email protected] (Please do not use email for other purposes exept for contacting me.)

I may not post chapters reguarly, because I may have lost motavation or got signed out of this account lol. Please be patient with the chaper distribution.

Thank you for listening! Bye my pookies!

~Harmony