Undertale Corrupted Justice is an AU where characters are shifted due to an alteration of events in the past, instead of for the sake of shifting characters.


In the beginning, everything was normal. Until one day, a human fell down. But it wasn't Chara. Instead, it was the human with the soul of justice. Asriel found him and brought him to his home. There the human saw Asgore and recognized him from a picture of the war. His grandfather died by his hands so he decided it was justice to avenge him. So in the middle of the night, he killed him. Toriel tried to stop him but ended up being killed as well.

After their king and queen died, the underground was in chaos. Asriel was too young to rule and didn't want it anyways. And then you had the issue of the human still being around. And more fell down over time. At last, they decided Undyne was the most capable and made her empress. She captured the human and killed him, and this was the first human soul. She then decided the other 2 humans who fell down in the meantime had to be killed as well, as well as all that followed, to protect monsterkind from their dangerous power and to escape the underground. However, Alphys wasn't happy with it and decided to go to the ruins to protect them from Undyne.

But with Undyne being queen and Alphys gone, the underground lacked a captain of the royal guard and a royal scientist, since Gaster was already shattered trough timelines, way earlier than normal since he was forced to work twice as fast. Sans was a logical replacement for him since he knew a lot about determination and timelines. He did create the Amalgamates but instead of quitting the experiment out of fear, he was just too lazy to continue. He did an experiment testing if they would laugh at his jokes though. Papyrus wasn't originally the candidate to replace Undyne but she decided to give it a try since she got annoyed by him begging for the position. Sans did an experiment that made him more capable since he didn't want him to fail and get openly laughed at.

Then you have Mettaton and Napstablook. In this timeline, Mettaton's body was an unfinished experiment of Sans he found at the garbage dump. Due to this, it's less powerful than the original one. They live in Snowdin due to the fact they needed a few more royal guards there and due to Napstablook and originally Mettaton are immune for physical attacks. They were excellent at human fighting, if it weren't for their personalities that hinder them.

Asriel left the castle sad about his parents. He went to the ruins to let himself die at the flowers at the entrance, were his mothers dust was scattered when Alphys stopped him. She told him the underground needed him. And if it wasn't as king, it was as a beacon of hope. So he became the star of the underground to prevent them from boring themself to death. And Chara? She was the 7th human, but she was the only one who didn't refuse Alphys offer to protect her since she didn't want to go back to the surface, since she still hates humanity. This meant Undyne couldn't take her soul and break the barrier, allowing the rest of the story to happen as normal as possible.


Undertale Characters


Alphys is the caretaker of the Ruins. She enjoys watching anime and Asriel's shows with Chara, usually while eating ice cream. She is a bit nervous, but way less than UT Alphys. She has a picture of Undyne in her room, and looks at it every evening. She is more happy than UT Toriel due to Chara's company. Theme: Can't we just settle down and watch Animé? (Heartache)


Chara is the 7th fallen human, with the soul of DETERMINATION. She likes to play with her knives and carve words and images in the walls. She is a bit sarcastic and likes to toy around with Frisk while they're in the Ruins. In her time with Alphys, she started enjoying anime, and her liking of Mew Mew Kissie Cutie 2 is disliked a lot by Alphys. In the endings where Alphys becomes queen, she gets the function of royal advisor. Chara is female in this AU. She is also one of the characters who needs to be SAVED in the Toriel fight. New role name: The Child That Stayed Role. Theme: A Rather Nice Demon (Ghost Fight)


Napstablook is located in Snowdin, and the first person you meet there. Instead of capturing the human, like Mettaton and Papyrus tell him to do, he rather makes music. He is not as depressed as in UT due to his Mettaton still being there, unless you kill him. He has 2 houses, Sans and Papyrus' old house in Snowdin and his original house in Waterfall, wich he often visits. He doesn't take any of Sans' jobs in Hotland. New role name: The Unwilling Judge Role. Themes: Spooky Tune-smith (sans), Song That Might Play When You Fight Napstablook (STMPWYFS), They might be smiling at another place (It's raining somewhere else), Ghoulovania (Megalovania)


Mettaton is located in Snowdin, together with Napstablook. Instead of wanting to become part of the Royal Guard, he wants to become the star of the Underground by capturing the human. He puts disco balls, speakers and tile puzzles all over Snowdin. He is not as powerful as UT MTT, and his box form is just very defensive instead of near indestructable. His secret style consists of items he uses in his UT shows. Instead of a scarf, he wears a pink cape. He's also terrible at baking steaks. Themes: Oh Yes YES! + robotrousle (Nyeh heh heh + Bonetrousle)


Papyrus is the lonely captain of the Royal Guard. Due to the experiment Sans did on him, he starts to hear voices, resulting in talking to himself. The only monsters that talk to him are Monster Kid and Napstablook, and Mad Dummy, who insults him every time he passes by. He believes Sans and Undyne have forgotten about him, which is untrue. In genocide, he turns into Disbelief Papyrus. New role name: The Conflicted Hero Role. Themes: Papyrus (Undyne), Run for the Great Papyrus! (Run!), NYEEEH (NGAAAH), Bone of Justice (Spear of Justice), But the Earth Grew a Spine (But the Earth Refused to Die), Battle against a Disbelieved Skeleton (Battle against a True Hero)


Sans is a lazy scientist, often quitting big experiments, like MTT's body, and the Amalgamates, out of lazyness. He usually watches Papyrus on his monitor when he is not busy inventing remote controlled machines, something he started to enjoy building. These machines take over his Hotland sentry post and hot dog stand. Unlike Alphys, he actually fights Frisk in genocide, using a remote controlled version of him. Themes: The grinning scientist (Alphys), This ain't a joke, kiddo (Alphys Takes Action)


Asriel is almost literally the star of the Underground. After his parent's death, he got a grudge on humanity, enjoying Frisks struggling in his shows. Outside of that, he always stays positive, and encourages others to do that too. Instead of wanting to leave the Underground with Frisks soul, he wants to give it to Undyne to break the Barrier and destroy humanity He has no box form, and instead uses a glorified remote controlled tv monitor with the exact same functions, and a face cam instead of the blocky screen. He has no NEO form either, despite facing you in genocide. He is in his adult form due to him never dying and turning into Flowey. He also is one of the characters that need to be SAVED in the Toriel fight. New role name: The Avenging Prince Role. Themes: Bright Colorful Lights! (It's Showtime!), Rainbow Maker (Metal Crusher), 5-star Hotel (Hotel), Can You Really Call This A Hotel The Lights Won't Go Out When I Flip The Off Switch (Can You Really...Or Anything), Death by Raining Stars (Death by Glamour), Power of HOPE (Power of NEO)


Undyne is the queen of the monsters. Originally she was very determined to kill the falling humans, but got unsure if it was the right thing when Intergrity and Kindness became her victims, both being complete pacifists, Kindness even willingly giving up her SOUL. She filled the throne room with Echo Flowers instead of flowers to remind her of home, but they ended up echoing the last words of the fallen humans. Themes: Lanzegerechtigkeit + Battle for your SOUL (Bergentruckung + Asgore)


Flowey is almost exactly the same as in Undertale, with the only exception she's female, and calls herself your best caretaker instead of your best friend. As Omega Flowey, she is a bit stronger than UT Omega Flowey due to the corrupting powers of the JUSTICE soul. Toriel itself is similair to Asriel, and gets corrupted in this form as well, after everyone is SAVED. Themes: Your Best Caretaker (Your Best Friend), Your Best Soul Destroyer (Your Best Nightmare), Hearts and Souls (Hopes and Dreams), SAVE the Corrupted World (SAVE the World), Her Theme (His Theme)


Asgore only appears at the end of Genocide, where he will tell you he really hates your route, but knows it was the only way to end humanity, right before he destroys the universe. Role name: The Slaughtered King Role. Theme: Revenge on Humanity (Megalo Strike Back i guess)

 Unshifted Undertale Characters


Frisk is the 8th fallen human, and the second red-souled one in a row. Frisk's gender is up to your own opinion.


Grillby's does not get visited by Sans anymore. Instead, Papyrus goes to eat there when inspecting the Snowdin royal guard.

Monster Kid

Monster Kid is now a fan of Papyrus, but complains a lot about the talking in himself. He tries all kinds of ridiculous ways to make him a bit cooler, but fails horribly.

Mad Dummy

Mad Dummy now enjoys bullying Papyrus. He has a bone stuck inside him, the result of Papyrus getting tired of it and never bothering to pull it out. The Mew Mew doll he ends up posessing was found in the Ruins when visiting the Ruins Dummy instead of in the lab.


Muffet has insomnia due to the constant flashing lights in Hotland.


He still hates his job, but Asriel treats him better than MTT in UT. He sometimes appears in his shows, either as a small cameo or comedic effect. He also follows an Acting for Dummies book written by Asriel.


Gaster fell into the CORE earlier than usual. Theme: Corrupt Corrupter Yet Corrupter (Dark Darker Yet Darker)

Added Characters

Papyrus' Voices

Papyrus has 5 voices in his head:

The Mean: This voice is similar to Underfell Papyrus and very mean to Papyrus and gets mad every time he does something wrong. He also thinks Papyrus is too nice, and helping weak monsters is a pathetic waste of time. In the Exiled Queen ending, he takes over Papyrus' mind almost completely.

The Classic: Papyrus' old self. Very optimistic and kind. He gets scared when Papyrus gets angry, and when he tries to kill Frisk. Believes everyone can be good, but dies off when Papyrus turns into Disbelief Papyrus.

The Cool Dude: Appeared when Monster Kid started following him. Wants Papyrus to be cooler than he is already.

The Cook: Continuously tries to convince Papyrus to make spaghetti instead of doing his Royal Guard Job.

Sans: Sans voice also haunts through his mind. It acts like he doesn't care about Papyrus anymore, which results him into thinking the actual Sans has forgotten him. Also makes Puns occasionally.


A robot made by Sans to guard the Hotland entrance. He has one fatal flaw: he's as lazy as his creator.


A robot made by Sans to sell hotdogs. Extremely good at putting them on heads, due to the fact it can fly.


A robot made by Sans to control the smaller Hotland robots due to a lack of arms. Is a massive controlfreak.


A robotic copy of Sans, purely made used to stop Frisk in genocide. Is way stronger than Sans, except for the fact he can't ignore invincibility frames or inflict Karma.

 Corrupted Justice

Corrupted Justice takes the role of the antagonist of the story. He is completely taken over by hatred, which allowed him to revive himself after his soul got taken. Due to him being monster nor human anymore, he can absorb any soul. He has no control over the timelines but seeing them. His preferbed weapon is a bow and arrow, as well as the souls of Toriel and Asgore he controls like puppets. After the 5th Genocide in a row, he takes out Asgore and attempts taking Frisks soul to rule over humanity as their savior. Themes: Battle between 2 evils (phase 1 theme), The Corrupted Justice (phase 2 theme)

Echo Flower: Justice is served. And whatever you do, you can't change it.

Roy (Bravery)

The second human to fall down, and the brother of Lisa. Usually peaceful, but never hesitated to fight when in danger. Before Undyne started the anti-human policy and ordered his soul, he and his sister lived in Snowdin.

Echo Flower: I see how it is... I won't give up without a fight, to save me and my sister!

Lisa (Perseverance)

The third human to fall down, and the sister of Roy. Fell down a few hours after his brother when looking for him. She was pretty shy, but managed to make a few friends among the monsters, before Undyne started the Anti-human policy and executed them.

Echo Flower: I-i can withstand this... C-can i?...

Thomas (Patience)

The 4th human to fall down. Stayed with Alphys for a long time, but eventually went to snowdin where the Canine Unit captured him and brought him to Undyne.

Echo Flower: I can't win. If i just wait, it'll be over quickly.

Suzy (Integrity)

The 5th human to fall down. After falling down, she escaped capture for a while, helping out the more peaceful monsters. When she tried to reason with Undyne, she quickly got killed though.

Echo Flower: I won't fight you. Noone deserves to die...

Lily (Kindness)

The girl who fell down before Chara. When hearing the tale of Monsterkind, she willingly let herself get captured for their freedom.

Echo Flower: Take my soul. Your kind deserves freedom.


Undertale Locations


On the walls of the ruins are many knife marks from Chara. The puzzles are also a bit more complicated, including some of Hotland's. Alphys' home is filled with anime posters and dvd's with anime on it, instead of books about snails.


Snowdin is filled with disco lights, music boxes and tile puzzles, to the annoyance of its inhabitants, who are getting a lack of sleep. The poorly made gates are replaced by orange lasers, and a sign saying not to keep moving trough them, written in a way that makes it obvious you have to do the opposite. The hidden room in Napstablook's and Mettaton's house now contains a music studio where some tracks from the Original Undertale are hidden.


Waterfall contains some more puzzles and poorly made gates from Papyrus' early days as the captain of the Royal Guard. Undyne's house is replaced by a Papyrus skull shaped building.


Hotland and the CORE have many billboards containing stars, rainbows and flashy lights, in an attempt of Asriel to bring more positivity there, but it mainly gives the inhabitants sleep problems. Remote controlled machines also are scattered trough the area, making life a bit more easy, but also creating new puzzles. Mettaton Resort is now Asriel Resort and has an Asriel statue with even more flashing lights instead of a Mettaton shaped fountain.

True Lab

The True Lab is mainly the same, but now contains one more room, this being the original hidden room below Sans' house.

New Home

The throne room now contains Echo Flowers, and Asgore's house is now Undyne's house.


  • The items related to the humans change, with the exception of Bravery's and Patience's.
  • The fallen human order is: Justice, Bravery, Perseverance, Patience, Integrity, Kindness, Determination (Chara), Determination (Frisk). Of the first 6, each one gets more innocent than the previous.
  • There now 8 characters that need to be SAVED in Toriel's fight, due to Chara's and Asriel's inclusion.
  • Face Steaks are replaced by Star shaped cookies (Star Cookies).

Soul changes

The monsters who can influence your soul are different. Napstablook and Mettaton now master the blue attack, Mettaton makes your soul yellow for some attacks, Papyrus is skilled in both green and blue, and Sans makes your soul yellow for Asriel. Muffet and Undyne still use purple and green.

Neutral ending changes

  • When Alphys becomes queen, Chara joins her as royal advisor. She also talks to Frisk in the flawed pacifist endings.
  • In the ending where Alpys is overtrown by Papyrus, who's lead by the mean voice in his head, Chara gets executed as the first of the new group of 7 human souls, putting Alphys in a depression and ending up with her commiting suicide. Sans believes his experiment on Papyrus was a mistake, since he's nothing like his brother anymore.
  • In the ending where Alphys is overtrown, but Papyrus is killed, Chara gets accidentally killed in the chaos, and Sans ends up storing her soul at a place it's safe from harm.
  • The ending where Mettaton becomes king is similair to UT's Mettaton ending, except Napstablook becomes his agent, as well as his assistant for his shows.
  • Mettaton's role in the other neutral endings changes as well from Papyrus'.
  • Papyrus has a less big hatred towards Frisk and humanity than UT Undyne in his endings, and simply continues Undyne's plan since it is what he believes was what she would want him to do.
  • Sans does not dissapear in any ending, and simply continues making remote controlled machines and scrapping big complicated projects.
  • Asriel's ending is actually more similair to Undyne's UT ending.
  • The circumstances to get Asriel's and MTT's endings are kinda reversed from UT's MTT and Papyrus endings. Asriel's ending requires MTT to be dead, while MTT's doesn't require Asriel to be dead.

Sub AU's

Underfell Fallen Justice

Justice did not attack Asgore and Toriel, and instead became the victim of a plan to frame him, and killed them in self-defense. Hence the AU's name change.

Asgore and Toriel decided to kill Justice and act like they got attacked in order to kick the Kill or be killed rule into action, but their plan failed and they died instead.

Flowey is a good guy, just like regular Underfell.

Alphys is less caring, and wants to keep the humans in the ruins so she can have control over them. She does not believe in the Kill or be killed rule, because she believes the weak monsters can still be useful as the servants of the stronger ones. An argument about it ended up in Undyne banishing her.

Due to CJ Chara being a neutral character, she stays neutral, with the positives and negatives swapped. She now tries to help Frisk go trough the Ruins, but it's because she wants them to leave asap, unlike in CJ, where she toys around with them but likes their company.

Napstablook makes edgier music and tries to keep control over Mettaton, because he wants him to become famous to ride on his success, and wants to make sure he never leaves him.

Mettaton gets bossed around by Napstablook, and hates being in the spotlight. He got forced into his body by him, and Sans put a trap inside it that activated when he became corporeal, resulting in a constant pain.

Papyrus is relatively the same as in regular CJ. He forced Sans to do the experiment, but he screwed it up on purpose, making him nicer instead of even more cruel. The only difference is the fact Monster Kid doesn't follow him all the time, since he hates him. The Dummy often talks with him.

Sans still makes remote controlled machines, but hides death traps inside them. He screwed the experiment up as revenge for the times Papyrus bossed him around.

Asriel was informed of the plan of his parents, and actively tries to keep it hidden. He still hates humans.

Undyne feels no remorse for killing humans, and completely believes in the Kill or be killed rule. She also hates it when others question her decisions.

Underswap Corrupted Justice

Just the swap version of this AU.

Outertale Corrupted Justice.

Corrupted Justice, but in space. Justice got there for a different reason than in regular CJ.

Inverted Justice

This sub AU explores the question what'd happen if the Toriel fight ended in the same way as Pre-IF's Asriel fight. The main difference is 8 lost souls swap instead of 6. Alphys was crowned queen, but didn't start the anti-human policy, until the monsters started rebelling against her, angering Undyne, who went to the Ruins to kill humans. Instead of telling him to become a beacon of hope, she kept Asriel in the Ruins to train as a human fighter. Sans became Royal Guard Captain to protect his brother, who became the Royal Scientist instead. He told Napstablook the little ghost had potential, and ignored MTT, who became determined to show the world he is the best of the 2. Chara made it past all of the guards, and with Papyrus' help disguises herself as an edgy robotic superstar, using the show name The CORE Killer.







  • There is no swap allowed where Chara and Asriel swap like in Storyshift, since it would not make sense with Chara's story in this timeline, and since the universe started as regular Undertale. The only exception is Inverted Justice, because that's something entirely different.
  • The characters don't make a perfect shift, due to Chara's and Asriel's positions.
  • There's no backstory on how the timeline was created yet, and there probably won't be one. Ever.
  • I have no idea how i came up with this idea lol.