"Long ago, two races ruled over Earth: Humans and Monsters." One race feared for their strong souls, the other for their magic, and the mages caught between them feared for both. All silently knew that war would be inevitable. The only thing that mattered was surviving it. One crimson mage understands that well, and is determined to keep herself and those she cares for alive.

after the sixth human died, Toriel couldn't endure watching another child fall just to meet their demise, so she asks sans to seal the entrance to the underground. stopping Frisk's arrival, the "system" glitches and tries to find a new host, the closest one he has is the judge of the underground: Sans the skeleton

In a reality where existence is a jigsaw puzzle of shattered worlds, a certain doctor has survived the collapse of his own universe and now embarks on a mission to build something new. Join one W.D Gaster utilizing the Observer, a creation of his own design, and navigate a realm where perfection is a mirage and every piece of a broken world holds the key to a bold new beginning.

After falling into the Underground, Frisk is found by a young Monster and taken home, where they find friendship and family, and make a new life for themself in the Kingdom of Monsters. But despite the happiness, something lingers in the back of their mind, and soon, they find a way to repay the kindness which they have been shown.

At the end of the war, monsters don't have the choice : they have to join Mont Ebott for survive another day. Sans and Papyrus, forced to run away after the attack of their village, are delivered to the horror of the war without any help and this one objective. But as sons of the royal scientist, W.D Gaster, they are an easy target. Both of them start a dangerous journey.

It's only thanks to you that I could change from a sadistic ogre to what I am now. I feel alive for the first time. I can't thank you enough, but I can write down my story. - This story follows Frisk and Chara from a genocide run to a truly happy ending!

Welcome to my diary! Written by me! THE AMAZING PAPYRUS! Read my totally cool adventures!

When Martlet goes to quit the Royal Guard, she gets a weird sense of deja-vu.

Littleverse: a multiverse in which most, if not all, of the main characters are children. Small children. Some of which have never had parents to guide them. FMD Ink: a psychopath. What will happen when these two forces meet? Well..a lot of adoption, fluff, and angst, apparently. We do not know how this happened. Go check out Clichély on AO3 and Wattpad!

The butterfly effect is known as "a property of chaotic systems by which small changes in initial conditions can lead to large-scale and unpredictable variation in the future state of the system." The smallest of changes make the largest of impacts. So… What if when Angel and Frisk fell… they fell into different locations? Squeal "One World, Two Souls", and "One World, Many Souls".

Sans has been teaching for a year and his second year of teaching is about to start. He didn't really have much expectations but that was until he became the teacher of Toriel's daughter, Chara.

A kid falls down a vast chasm into the deep, and is set upon by countless monsters eager to murder whoever falls down and claim their souls. Somehow, this child is the villain in your story.

The Underground is divided. Evil lurks in the darkness as hope slowly fades away. Only a human, a monster, and a dead prince can restore this corrupt kingdom, but not if it corrupts them first.

A young man named Aiden is plucked from his own reality, and brought into the world of Undertale by Gaster, in an effort to stop his world's destruction. When he comes across a genocidal Frisk, Aiden chooses to fight in order to stop them. After all, fighting's one of the few things he knows best. (Based off of XWolf26's DoubleTale. Rewrite of DoubleTrigger.)

"El jugador" ha muerto... Y ahora todos quieren JUGAR. En la peligrosa Ebott City, radica una constante inconformidad por habitar monstruos y humanos en un mismo lugar., desatándose conflictos delictivos que atentan con la vida de los habitantes. Sin importarle las advertencias de su madre, Frisk decide ir a la ciudad y tener su florería junto con su compañero y mejor amigo Flowey

For Monsterkind, the Surface represented freedom. For Frisk, it's a return to some uncomfortable realities. It all began with a simple wish. When that wish faded, Frisk tried to move on. Except, 'moving on' was not so simple. Emerging from the Underground had put them in a worldwide spotlight. From an unknown child, they had become an icon of great value.

Frisk no longer exists. Chara has become the main character. After 1000 years of genocide, something new happens, and Chara is thrown into a whole new underground. Will Chara manage to survive this new environment? Well, let's see how much determination they'll have after exploring the new routes this new game has to offer! Rated T for minor adult themes.

After Frisk's father died when she was eleven and her mother became heartbroken Frisk swore she would never fall in love... until she meets a very punny skeleton named Sans.

After leaving the Underground, Frisk and the monsters begin their journey down Mt. Ebbot to face the surface world. As they navigate their new environment, tensions arise between the monsters and curious but cautious humans. Frisk is reunited with familiar faces from their past, including an old caretaker, Lena, and some friends from the orphanage.

A household full of skeletons are competing over the attentions of one love. This isnt that house though. Unknown to the group secretively wrestling with their unpredictable love lives and universe-meddling machine, another house a few doors down has been gifted with its own skeleton posse clamoring for the attentions of their own little lady. A little old lady by the name of Mabel

Tired, overworked, a alone in a new city Y/N is living on muscle memory and cup ramen. How will she cope when four trouble making bitties make their way into her life? They've been through hell and back, left with no hope of a home what will happen when they meet a reckless human with more determination than could ever be safe?

You are dropped into the underground world, home to many monsters when a very voluptuous goat mom approaches you and takes you in. There are many mysteries centered around you. It is up to you if you wish to uncover them. This thicc monster lady would like to help, but she wants quite a bit from you. Will you be able to satisfy her overwhelming needs like her husband? Could what yo

Во время битвы между Фриск и Омега Флауи происходит некая странная ошибка, в итоге которой... Фриск и Флауи вынуждены не просто объединится, а научится действовать синхронно и слажено, без ссор и ругани, если они хотят выпутаться из их ситуации...

After doing everything the right way in the first timeline, Frisk was compelled to do the genocide route for what they felt were "good" reasons. In doing so, they have broken utterly and become something new. Something absolutely devoted to Sans, and not remotely sane. Now they are striving to fix everything and find their path forward. What the hell is Sans supposed to do now?

Humans and monsters a slowly leaning to live in harmony again. However, many humans harbor a myriad of reasons to distrust monsterkind. As if being the ambassador to humanity wasn't hard enough, an extraterrestrial threat looms on the horizon. With the help of a being known as Dragon Lord Tao, Frisk and her new family must face new foes far more malevolent than any monster.