This is a sequel to my old story, Integritale, which you will find in my profile. I don't know if this could be considered an AU to the Undertale Universe, since I did add a lot of stuff, but still tried to adhere to the canon as much as possible. In any case, please, enjoy! Any feedback is welcome!

Sans tries to use a new strategy to save his world from the being that is trying to wipe out all of monsterkind. This backfires tremendously when a human from the real world (that doesn't even know about Undertale) gets transported into his universe. Will this result in friendship, a game of cat and mouse…or the absolute?

After a tragic accident, a young boy named Vance wakes up in the world of Undertale his favorite game. Reincarnated as a human with magic powers, he finds himself living alongside the monsters he once knew only from his screen. With familiar faces and unexpected adventures around every corner, Vance explores the Underground.OC Harem Fic include characters from Deltarune/ UT Yellow

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".

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!

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.

[Horrortale AU] After their fight against Omega Flowey, Frisk left the Underground to get help and save their friends. Unfortunately, humans are not as comprehensive as monterkind and they didn't believe them. How to change their mind ? In the Underground, the situation is getting worse. Toriel and Undyne are fighting for the throne, and chaos is taking place in the Kingdom.

Asriel is miraculously revived and is living happily with Frisk, Toriel, Asgore, and the other monsters. But Frisk has a secret, and Chara is tormenting them for it. 3 years later, they go back to Ebott and help Chara regain their compassion after having an empty soul for so long. A year after, Frisk is still the tiniest bit resentful towards Chara cuz..y'know. Fem Frisk Male Chara

In the wake of the human's devastation, Papyrus was made king, and his brother Sans was made to suffer the consequences of his own inaction. Papyrus has a lot to live up to, and as time goes on he is forced to face the past and make a grave decision for his people's future. (Speculative story about the King Papyrus neutral ending).

Just because your father is "Renowned Scientist Dr. W.D. Gaster" doesn't mean everything in life goes according to plan. Corbel H. Gaster knows this entirely too well. If trying to balance school, friends, and a life-altering disease wasn't hard enough, Corbel must also face the pressure of living up to his father's legacy. AU story for "The CORE of the Matter" CONTAINS SPOILERS!

Short stories set in the VOXISTALE universe.

A Multiverse Phenomenon drags Nightmare to a place that should be unreachable. Yet it changes the course of this Multiverse irrevocably.

"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.

The story is set in a generic alternate timeline where Frisk said "Nah." and brought Asriel back to the surface anyway. Asriel, thrown into a middle state between the adult form he had exhibited before and the child form of his past, has adjusted fairly well, as did most of the Monsters that chose to move aboveground. Meanwhile in the Underground, a new faction has appeared.

"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

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.

Deltarune, but with Muffet. It's very short because I want to go to bed. Also it wouldn't let me pick Deltarune as a category. Sorry.

Gaster 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. Worse, they would start to destroy each other. He had to make things right, stop the resets, and to do that, he had to leave the Void. UPDATE 2024: NEW EPILOGUE!

This takes place after the genocide run, where Chara will be fighting with Frisk. Also Chara and Frisk are both girls in my AU and As the future awaits, what choice will Frisk takes? RESET? SAVE? will they fall in the same situation again? or maybe things will be different this time. . . (also the cover is made by me!)

THE END AND BEGINNING ARE ONE POINT IN DARKNESS. It Was The End. It was The Beginning. Every World is collapsing, and one is the Support. Holding every timeline, every consequence, UNDERTALE's World is in for a rude awakening. The Three Heroes set out to find the root cause of this mess, with one clue, "Banish the ANGEL'S HEAVEN." But in the end... Do their Choices Really Matter?

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.

In a scrambled timeline, Frisk has carved a dusty trail through the underground countless times, and a scattered scientist has had enough. He gambles on pulling a human from beyond his reality to try and finally stop Frisk. He's hedged his bets on...this sleepy-lookin' girl lugging around a bootleg sword to go fight a squinty kid in her pajamas. This timeline's doomed.

After the death of the sixth human, Toriel makes a desperate request: seal the entrance to the Underground. Sans reluctantly agrees, but stopping Frisk's arrival sends the system into chaos, and the soul of Determination finds a new host—Sans himself. Now burdened with immense power, a destruction-hungry phantom, and an unquenchable thirst for Determination, how will Sans navigate

Eran las primeras vacaciones que se tomaba. Sans pensó que serian relativamente tranquilas, claro, si se ignoraba los gritos de su hermano, Papyrus, y el enamoramiento de este con Frisk; la molesta y deportista Undyne, intentando que se levantase del sofá y moviese el esqueleto; además de la familia Dreemurr, conocia a Toriel, pero sus hijos eran otra cosa. [Chara x Sans] Resubido

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.