*Have you thought about a world where everything is exactly the same...
*Except you don't exist?

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Tyrannic Fell is an AU where Asgore became mad after monsterkind's defeat, and got a hatred for the weak monsters that in his eyes caused their loss of the war. He started to rule with an iron fist, ordering the execution of weak monsters, and everyone who rebelled against him suffered a terrible fate. Gaster, Asriel and Chara are all alive in this AU, as the events relating to them are heavily different. This AU is slightly inspired by Despotale, but with the Fell theme present in Underfell, Underfoil and especially Negativetale.



Frisk is the 8th human to fall down, and the one who will end the cruelty of the monsters, either by killing them all or trying to teach them kindness.


Flowey is your typical Fell Flowey, scared, helpful towards Frisk and traveling in their pocket, but with one big difference: he is created from the dust of Monster Kid. He never turns into his Omega form, but instead compliments Frisk with defeating Asgore. Theme: Your Best Minion (Your Best Friend)

"Y-you're not going to kill me? T-thanks, but i warn you, the others definitly will try to kill YOU. That's how it goes here, it's kill or be killed."

Ruins Dummy

The Ruins Dummy is used by Flowey to teach Frisk fighting. It is heavily beaten up, covered with cotton, and has a knife stuck in its head.


Asriel was born a few weeks before Toriel escaped the clutches of Asgore and went to the Ruins to rebel against him. His father raised him to become a merciless tyrant, and he became cruel, enjoying the suffering of others. When he became an adult, he was tasked with the capture of his mother, and executing the weak monsters living in the Ruins. After a long battle he defeated her, chaining her up in her former room and turning the Ruins into a prison made for weak monsters to be served their death sentence, usually killing them in front of his mother. The only monster he spared was Loox, who he enslaved to give information about the current status of the Ruins. He also decided not to kill Chara, and instead enslaved her as well. Themes: The Executioner (encounter theme), Heartless (Heartache)

"The weak are not just traitors, but also useless, and thus a waste of resources. For every weak monster killed, a strong one's life will improve. For monsterkind's sake, i can't be merciful, even if i wanted to."


Chara is the 7th human to fall down, and instead of bringing her to the king, Asriel decided to keep her as a slave/pet. She looks mostly the same as Undertale Chara, though she's more beaten up, and has a spiked dog collar around her neck, put on by Asriel to zap her when she misbehaves, or when he just wants to see someone get hurt. She fights Frisk in the place of Napstablook. During the Asriel fight, she frees Toriel, who then defeats him. Theme: Knife to Meet You (encounter theme), Knife Abuse (Ghost Fight)

"I used to hate humanity, but to be honest, now i sort of miss them. Even if they are mean and abusive, they at least don't treat you as a pet."


Tyrannicfelltoriel aftersaved

Toriel after Asriel's defeat. Sprite by Meme Sans

After many years she escaped her husband, and fled to the Ruins to rebel against him and protect the weak monsters. 18 years later though, she was defeated and captured by Asriel, who chained her up in her former room. In the years she was imprisoned there, she was heavily abused, one of her horns is cut in half, and one of her horns is entirely pulled out, and used to take out her left eye. Her clothes are ragged and full of dust, and her body is covered with scars. She gets freed by Chara during the Asriel fight, and defeats him, taking back the control over the Ruins.

"I know you want to leave, but i warn you, if they get your soul, then not just the Underground will be a hell, but the outside world too..."

Sans and Papyrus

To help them survive the cruel world of Tyrannic Fell, their father Gaster raised them to not feel anything for anyone except him, each other, and their king. Due to this they are way more antagonistic, cruel and murderous than their Undertale counterparts.

Sans is a cruel, usually emotionless asassin, having a similair appearance to Dusttale Sans. In most of his Snowdin encounters, he remains hidden, attacking Frisk from behind the trees, but in Waterfall and Hotland, he reveals himself, trying to intimidate Frisk (N), openly showing a hatred for them (TP), or complimenting them for killing all the "useless monsters" (G). Instead of his normal bones, he usually uses arrow-like sharpened bones to attack. He is fought in the Judgement Hall in all 3 routes, in Neutral to protect his king (and if Papyrus is killed to avenge him), in True Pacifist out of pure hatred, destroying the MERCY button to force Frisk to fight, showing the monsters following them they weren't all peaceful, hoping to revert them to their former selves, and in Genocide out of self-defense, and to avenge his brother. Despite this, Genocide is the only route he can actually be killed in. Themes: The Asansin (Sans), Song That Plays When You Get Attacked From The Shadows (STMPWYFS), Cruelty (Neutral Megalo), Hatred (True Pacifist Megalo), Corruption (Genocide Megalo)

"I sense you have killed others, just like me. I also sense you enjoyed doing it. You're just like us, a killer. You cannot deny the truth. Just admit it..."

"You have chosen the pacifist way, but have you ever thought about killing? It feels better than you'd expect at first, and when you've started, you'll want more and more..."

Papyrus is very similair to his Underfell counterpart. He is the captain of the Royal Guard, and rules Snowdin with an iron fist (almost literally, as his gloves are filled with steel for combat), execution everyone who is too weak or disobeys him. He filled the forest with death traps, and many bones still stick out of the ground as remains from the many times he attacked someone. He attacks Frisk at their first encounter, but stops when realizing it's more fun to use his death traps. During his fight, he uses his gloves for attacks as well. Themes: Nyeh, Heh, Heh... + Iron Fist (Nyeh heh heh + Bonetrousle), Torture Start/Tense/Fight (Dating Start/Tense/Fight)

"There are 2 kinds of people in the world: those who control and those who are controlled. Those who refuse to be controlled only have a place in the afterlife... The deepest, most hellish part of it, that is..."

Canine Unit

The Canine Unit is completey under Papyrus' control, and blindly follows his orders. They still have their original personalities deep inside though. Theme: Dogbite (Dogsong)


Rudolph tried to take over control over Snowdin using democracy, however, he quickly got arrested and gets executed when Frisk arrives. The original plan was to execute his daughter with him, but Noelle fled to Waterfall and now lives with Susie, wich is the only reason Undyne hasn't killed her yet.


Grillby's closed long ago, and he lives in the remains of it. He's extremely depressed, and is almost completely forgotten by everyone. When Frisk visits him, he turns mad, and tries to kill them for their soul. Theme: Ashes to Ashes, Dust to Dust (battle theme)

"Souls burn bright... Very, very bright... Sweet little fire... BURN IT, BURN IT!!!"


Undyne never joined the guard, and became a hitman instead. She's usually tasked with hunting down weak or rebelling monsters, often killing them, and is the cause of Monster Kid's death. She has a large scar over her eye, but decides not to wear an eyepatch over it. In True Pacifist, her pure hatred for Frisk's pacifism turns her into Undyne the Hateful, and has to be fought until weakened enough and Susie stops her. Themes: Run or Die! (Run!), Spear of Terror (Spear of Justice), But The Earth Doesn't Show Mercy (But The Earth Refused To Die), Battle against an Insane Killer (Battle against a True Hero)

"Why do you keep sparing weak monsters?! Our lives would be a whole lot easier if you just would've killed them! NGAAAAH!!!"


Aaron wants to join Undyne and Susie, though they won't even allow him to get near him, and he still got a spear stuck in his chest from the last time he tried.

Determined Bird

The Determined Bird hides near the dump, as Undyne and Susie try to hunt it down because Gaster orders his capture, as he thinks it holds actual determination, and wants to dissect it to see how. The place he used to be at now contains a bridge.


Susie is Undyne's partner, and loves to beat people up, usually for no reason. She's encountered at the dump where she is beating up one of the snails from the Blook family's old snail farm, but let's him go when she notices Frisk. She has a slightly more evil looking version of her Dark World design, and uses her axe in battle. She doesn't actually believe in Asgore's policy, but joined Undyne "cuz it's fun". She lives in Mettaton's old house, where she has a hangout. Themes: Bullying the Bully Back (Dummy!), Trash Party (hangout theme)

"Look, i don't care about if weak monsters should live or die. I just won't let a chance to beat people up go, especially not if i get payed for it as well."

Madboo and Dulley

Madboo is an agressive ghost encountered in Waterfall. He once lived in Papyrus' training dummy, but when he got discovered, he was kicked out, and eventually went on to live in Napstablook's abandoned house. In True Pacifist, he later on finds a Mew Mew doll in Gaster's trash can, and posesses it to become Glad Mew Mew, and is an optional boss when returning to his house. Themes: Mad House (Pathetic House), Glad Mew Mew (Mad Mew Mew)


Dulley used to live in the dummy in the Ruins, but left it when Asriel and Chara, wnd later Flowey recked it, and now lives with Madboo. He doesn't say much, aside from a single "Hi..."


The Temmies were seen as a treath by Asgore, so he fed them modified Tem Flaked until they got into a constant state of hallucinations. Themes: TeMiE VwiLlAg (Temmie Village)


Gerson is one of the few monsters not corrupted by Asgore, having seen the truth of the war. He went to Temmie Village, where he helped getting the Tem Shopkeeper and Bob out of their hallucinations, and together with them opened a shop in the village. Theme: Gerson Shop (Tem Shop)

"This world is one built on lies and deception. If our king would've known the true events that happened in the past, he'd be a better man. Though maybe the queen would've caused trouble then, wahaha!"


After her sister got taken for the Monster Improvement Experiments, she feared for her life, and ran towards the river, where she discovered the remains of a fight and a boat. She decided to use it to ferry across the river, her sad song being able to be heard from miles away. Theme: Shyren's Song (river area theme)

"Music is the easiest way to forget you live in a nightmare, but even that won't heal the wounds of the past..."

Gaster and Alphys

Gaster is a diabolical scientist, and Alphys is his slightly less diabolical assistant. They are very cruel, often plucking a random nearby monsters from the street to experiment on them. The time that happened the most is known as the Monster Improvement Experiment Era.

Alphys still likes anime, but is very secretive about it, as Gaster absolutely hates such "dumb time wasting entertainment", and has a scar on her face from when he discovered her owning a Mew Mew doll, wich he considered childish. Her glasses are replaced by a futuristic vizor with infrared vision and zooming function, wich Gaster originally made for Mettaton, but he rejected it so she took it instead. Theme: Frankenlizard (Alphys)

"A-anime may seem childish to you, b-but it distracts from the h-harsh reality! P-please Gaster, d-don't do thi-AUCH!!!"

Gaster is very calculating, believing all forms of entertainment are useless, and only allowed the creation of Mettaton like he is today to make Alphys happy, as despite his hatred for her anime, she was one of the few monsters he cared about. Unlike in Undertale, the Amalgamates and Flowey were created on purpose, hoping to make weak monsters stronger, and with success, as the Amalgamates are near indestructable and Flowey managed to escape the lab. However, Asgore never acknowledged his efforts, turning him bitter and even more cruel, starting to get a grudge towards his assistant who was getting all the praise for creating Mettaton. In Neutral and True Pacifist, he is fought in the lab instead of Mettaton, who's quiz is moved to Mettaton Resort. In Genocide, he destroys him, and uses his machine parts to enhance himself, replacing Mettaton NEO. If the Genocide is aborted in Hotland/CORE, he doesn't fight Frisk. Themes: World Dominator Gaster (encounter theme), Dark Darker Yet Murderer (N/TP battle theme), Power of SCIENCE (Power of NEO)

"You can only trust yourself, and your closest relatives, as everyone else WILL betray you at one point. Some will even have done it without you noticing..."

Mettaton and Napstablook

Mettaton is very unloyal, usually following the one with the most power, something that ends up in him getting destroyed by Gaster when trying to ally with Frisk in Genocide, wich leaves him with only his head, wich gets insantly destroyed when interacting. He has more weapon functions than his UT counterpart, wich he uses to make his shows much more "exiting", by using them on his participants. Aside from his 2 arms, he also has 4 Swapfell Napstaton-esque floating hands, and his true form is called Mettaton EXE. Themes: Death Report/Even More Death Report (Live Report/Death Report), A Show to Die For! (It's Showtime!), Diamond Pulverizer (Metal Crusher), Eradication by Malice (Death by Glamour)

"The path to success is not being good at something. It's knowing who to follow and being able to switch sides without regretting it."

Napstablook used to live with Mettaton, but when he saw what he became, he left him. Mettaton got angry, and ordered Alphys to capture him and trap him in his body. He is now stuck there, and only Mettaton can hear him. After True Pacifist, Alphys upgrades Mettaton's body, giving him his own head, and in Genocide, he escapes during the Gaster fight, making the machine parts malfunction and Gaster vulnerable. Themes: Ghoultune (Spooktune), Ghoulwave (Spookwave)

"I have been trapped so long, but thanks to you, i'm finally free! Alphys, i'm coming for you, so you'll better hide..."


Muffet is hated by nearly everyone, as Asgore put her in charge of the Spider Spionage and Taxes Network, wich looks for any potential rebellion and collecting extremely high taxes from the citizens in Hotland and New Home. The power got to her head, and she acts like she's royalty itself, crowning herself Queen of all Spiders. Her bake sale is ran by a bunch of spiders, as she never leaves her throne made out of spiderwebs. She is rumoured to have a crush on Asriel, though noone knows if it's genuine or only to get a true royal position by marrying the prince (spoiler: it's the latter one). Theme: Spider Dance For Your Life (Spider Dance)

"Ahuhu, you made a poor choice by coming here. But then again, it was your only one... Your soul will be the final ingredient for my -metaphorical- web i span across the Underground. With your soul, i will truly be a queen..."


Gaster built a robot to take Burgerpants' job, as robots don't need money, complain, or talk with customers. It also has anti-human weapons, wich it uses in Genocide.

Gaster Followers/Goners

The 5 Gaster Followers/Goners were the most successful True Lab experiments, and turned into Gaster's most loyal helpers. They are tasked with protecting the CORE, only allowing a select few to enter, and eradicating anyone else who attempts to. Their code names are 9_Child, 10_Clamp, 11_Head, 12_Eyes and 13_Facecarrier. Goner Kid would've been executed like her brother Monster Kid if Gaster didn't want her alive for the Monster Improvement Experiments. Theme: Attacking the CORE (battle theme)


Jerry is trapped in the CORE, used by Gaster to boost the power of Goner Kid, the weakest of Gaster's CORE defense group. He can't be ditched, though can be killed to stop his boost.


Red is one of the more kind people, though it didn't stop her from joining the guard. She commands the New Home section of the Royal Guard less strictly than the other commanders. She doesn't like Asgore's policy, usually secretly trying to protect and help the weak monsters she is supposed to capture or kill, though she still has killed a fair amount, usually when Asgore was inspecting her and other similair situations. She is very deadly if she wants to, like in Genocide, having a very diverse amount of weapons at her disposal. Themes: Blood Red (N/TP battle theme), Red of DETERMINATION (Geno battle theme)

"Even if the world is a living hell, don't hesitate to do good if you can. Even if you end up death, it's better to die for a noble cause than living as a monster... You know what i mean."


Asgore believes weak monsters are useless, and blames them for the loss of the war. The exact reasons for this are unknown to most monsters, though Gerson knows it's because his father died protecting a few of the weaker monsters, and someone unknown to him with evil intentions corrupted the tale, making him believe they sacrificed him for their own safety. He rules with an iron fist, torturing and executing those who disobey him or he considers useless. After his defeat in Neutral, Frisk takes his soul and leaves, and in True Pacifist, he gets overtrown by Toriel and after the barrier is broken locked up in the Ruins together with Asriel. Themes: The Tyrant + Showdown With The True Villain (Bergentrucking + Asgore)

"The weak will act nice and all, but the truth is, they're parasites. And what do you do with parasites? You kill them."

Test Subjects 1 - 7 (Amalgamates)

The Amalgamates are the same as in Undertale, except they're give the code names 1_Memory, 2_Dogs, 3_Food, 4_Bird, 5_Man, 6_Freeze and 7_Stick. Themes: There we Were (Here We Are), Amalgam (Amalgam)

Test Subject 14_Burger (Burgerpants)

After Burgerpants was replaced by a robot, he got taken for the Monster Improvement Experiments, where they tried to give him ghost properties. This failed, and he became very messed up. Theme: Can You R34lly Call This A Gh_st... (battle theme)

"3ven b__ng 4 MTT Res0rt employ33 is am_z1ng c0_pared to th1s..."

Test Subject 15_Tentacle (Onionsan)

Onionsan is locked up in an aquarium in the True Lab, after he got turned into a vicious monster during the Monster Improvement Experiments. He attacks anyone who comes close, and devours them alive. Theme: Tentacled Horror (battle theme)

Test Subject 16_Bones (Grandpa Semi)

Due to his old age, Gaster decided his father wasn't useful anymore and decided to use him for the monster Improvement Experiments, trying to make him stronger and enhance his lifespan. While the second thing did happen, it made him a lot weaker instead, turning him into a living pile of bones, barely able to move and talk.

"Appearantly... Even... Your... Own... Son... Will... Turn... Against... You... At... Some... Point..."

Test Subject 17_Apology (So Sorry) and Test Subject 18_Doodle (Doodlebog)

So Sorry got taken for research purposes, as he wasn't of any known monster species. He died during one of the experiments, and his dust now remains in a jar in the lab. In the lab, So Sorry accidentally created a Doodlebog, wich now roams the True Lab. Alphys and Gaster tried to catch it, but with no success.

Monster Kid

Monster Kid got killed by Undyne because he was weak, and on Alphys' demand, his dust was gathered for experiments, spread across a flower and injected with Determination, turning him into Flowey. In True Pacifist, as Flowey he tries to break the barrier using the souls, but when turning into his true self, a massive anger and hatred grows inside of him, and he decides to destroy monsterkind, forcing Frisk to stop him. Themes: His Track (His Theme), Bad Dreams, False Hopes (Hopes and Dreams), DESTROY the World (SAVE the World)



Dohj was one of the highest ranking members during the war, and when Asgore's father died, she used this to her advantage to manipulate Asgore and become the true ruler of the Underground. She failed however, as Asgore killed her in his rage. She takes Chara's place in Genocide.

"I helped the king with creating a great world, and he killed me! This world deserves to be destroyed..."

River Person

The River Person was supposed to be taken for the Monster Improvement Experiments, but escaped, and jumped in the CORE, leaving a note saying noone else should be able to use his power. Theme: Mysterious Mystery Yet Mystery (Dark Darker Yet Darker)

"My power is too dangerous to be used for evil. You will never see me again, as i united with the void."



The Ruins are empty and dead, all leaves having withered, and dust getting blown trough the corridors. Only a few people live here: Flowey, Loox, Asriel, Chara, Toriel and a few spiders. The rooms up to the Dummy room are blocked off from the rest of the area by vines created by Flowey to stay safe from it's cruel executioner, and the puzzles aren't changed too much, though slightly broken, and the walls are covered in vines as well. The rooms after that are under Asriel's control, and are filled with death traps containg spikes, knives, and in one case even the ceiling dropping down crushing it's victims trying to get a Monster Candy. The Spider Bake sale is still present, and used by Asriel to receive information from Hotland and New Home. Many people outside call this place the Death Chambers. Themes: Flowey's Shelter (Flowey's section), Ruins of Despair (Asriel's section)


Snowdin Forest is filled with bones and death traps, and between the trees at the Ruins entrance, Sans created passageways and holes to attack from the shadows. No monsters live in this area, as coming there unprepared basically is a death sentence. The town itself is just as bone filled as the forest, a guillotine with a bone as blade stands in the middle of the town, most houses are very broken down, the library is completely burned to the ground, and Grillby's is turned into ruins. The only house that's not run-down is Sans and Papyrus', wich is turned into a fortress surrounded by bones, and Papyrus' shelter is replaced by a cage made of bones. Themes: Dusty (Snowy), Snowdin Hell (Snowdin Town)


Waterfall isn't too different from Undertale, though Sans' telescope is nonexistant, the small gap has a bridge blocked from one side, the Blook area is run-down, Gerson's shop is abandoned and a bunch of dust piles are scattered troughout the area. Theme: Dusty Falls (Waterfall)


Hotland is under Gaster's and Muffet's control, and is very tough to live in, with the experiments happening in the True Lab and Muffet's spionage network and extreme taxes. The laser puzzles and Mettaton' shows are much deadlier. The mayority of the CORE monsters appears here, with the exception of Knight Knight. Theme: The Only Medium (Another Medium)


The CORE layout is completely different, having 5 rooms guarded by the Gaster Followers, with switches that open a heavily armored door. Only a select few are allowed to enter here. Theme: (CORE)

New Home

New Home is significantly bigger than in Undertale, being a death trap filled maze. Knight Knight and the hard mode exclusive monsters are encountered here. Theme: Approaching the Castle (New Home theme)

Misc changes

  • Flowey calls Frisk instead of Sans.
  • Flowey's code name is Test Subject 8_Flower.

Neutral endings

  • The Weak Peace Ending: in this ending, no monsters are killed: Toriel becomes queen and tries to turn the Underground into a better place. When Flowey calls, the mayority of the Underground has been cleaned up, though the Ruins are controlled by Asriel and a small group of rebels preparing to start a civil war. Unlike canon Undertale, Toriel still wants to gather souls, though spares Chara.
  • The Civil War Ending: in this ending, only a few monsters are killed, none of them being mayor: Toriel becomes queen and tries to turn the Underground into a better place, but a big group of monsters, including Sans, Undyne and Muffet, ignore the new policy, and continue attacking weak monsters, forcing Toriel to expand the Royal Guard, with Red as its leader. Unlike canon Undertale, Toriel still wants to gather souls, though spares Chara.
  • The Relief Ending: in this ending, all killable mayor monsters are killed, though no minor ones: Toriel becomes queen, and tries to turn the Underground into a better place. After the confusion why most important people dissapeared, the weaker monsters believe Frisk was sent to free them from their tyrants, and start worshipping them as a deity. Alphys seemingly becomes loyal to Toriel, while Sans hides in the Ruins in anger. Unlike canon Undertale, Toriel still wants to gather souls, though spares Chara.
  • The Corrupted Queen Ending (has multiple sub endings for certain characters being alive or dead): in this ending, a bunch of monsters are killed. Asriel and Muffet are the only mayor ones required to be alive: Toriel becomes queen, but a rebellion starts and Asriel takes over the throne, re-capturing Toriel and Chara. Asriel and Muffet get married, but Asriel dies in a mysterious "accident" leaving Muffet to rule. Monsters are homeless and starving as there are massive taxes on basically everything, and those who complain get captured by spiders to serve as their queen's dinner. Toriel is released from her prison to serve Muffet, and Chara wasn't killed for her soul as the new queen doesn't want the barrier to be broken, but a bunch of monsters killed her anyways for food.
  • The Returned Heir Ending (has multiple sub endings for certain characters being alive or dead): same as ending 3, but Muffet has to be dead: Toriel becomes queen, but a rebellion starts and Asriel takes over the throne, re-capturing Toriel and Chara. Nothing big changes from before, as Asriel rules the same way his father did. However, depending on who is alive and dead, new people are put in charge of the other area's, and Flowey takes full control over the Ruins as a safe haven for the weak monsters.
  • The New Tyrant Ending: (multiple sub endings): Asriel has to be dead, and Papyrus and optionally Gaster must be alive: Toriel leaves the Ruins, but gets ambushed and killed by the skeleton brothers, who take control over the Underground. Chara's soul gets taken, and the new kings decide to clean up the Underground of any possible threaths, ending up in the executions of many, including Undyne, Gerson, the entire Temmie race, Mettaton, Muffet and her pet, and Red, if they're not killed already. Gaster becomes the commander of the remains of the Royal Guard if he isn't killed yet, Alphys becomes the Royal Scientist, and the remaining monsters become slaves.
  • The Experimental Ending (multiple sub endings): Asriel and Papyrus have to be killed, and Gaster must be alive: after the king's defeat Gaster claims the throne, and together with Alphys and Sans, he turns the Underground into a scientific dystopia. The True Lab experiments get released, as the True Lab needs to be used for new experiments, and the Amalgamates and Onionsan are used to keep the citizens in line. Toriel, Flowey and Chara live in the Ruins together.
  • The True Civil War Ending: requires every mayor character to be killed, except Undyne and Mettaton, and optionally Muffet and Susie: Undyne kills Toriel when she tries to take the throne, and takes it herself. Mettaton had the same idea though, and a civil war starts, with Mettaton and Alphys controlling Hotland, the CORE (wich overheated as Undyne stopped the production of ice to cool it down) and New Home, Undyne and Sans controlling Snowdin and Waterfall, and Flowey and Chara sort of controlling the Ruins, wich means just themselves and the spiders.
  • The Despair Ending: requires every mayor character to be killed, except Undyne, and optionally Muffet and Susie: Undyne kills Toriel when she tries to take the throne, and takes it herself. However, she's a poor ruler, and the Underground slowly crumbles. Alphys falls into a depression after both of her friends died, and lets the True Lab subjects accidentally escape, resulting in Onionsan turning Waterfall into a hell.
  • The Celebrity Ending: requires every killable mayor character to be dead, except Mettaton, and optionally Susie and Muffet: Toriel tries to claim the throne, but gets attacked in the CORE, wich Mettaton has taken over, and she and Chara get executed during a live broadcast. With Mettaton as king, the Underground turns into pure madness, as Mettaton abducts random monsters to participate in deadly tv shows and forces everyone to build statues of him.
  • The Corrupted Queen Ending 2: same as the first, except all mayor characters but Muffet and optionally Susie are killed: Muffet takes the throne and rules the same as in the first.
  • The Anarchy Ending: requires every mayor character to be dead except Susie: with nearly everyone important killed and Sans and Toriel going into hiding, Susie sort of takes over, though it only strengthens the state of anarchy, as she constantly beats up and enslaves people she doesn't like.
  • The Chaos Ending: requires every killable mayor character and at least one other monster to be killed: Toriel and Sans both try to take over, but the angered monsters don't like their policies and kill them both. To prevent chaos, Flowey takes over the throne, and creates a very unstable peace.
  • The Insanity Ending: the ending that happens if a genocide route is aborted in Hotland/CORE: Gaster takes control over the remains of Monsterkind, but Napstablook nearly kills him during one of his many attempts to escape. Turned insane by the long time he has been trapped there, he takes over the throne from him and orders Alphys to create the ultimate robotic body for him, which when finished he uses to blast her head off as revenge for her assisting in trapping him in his cousin's body. After this, he rules the Underground like a madman, blasting everyone who disobeys him into oblivion, and threathens to kill Gaster just so Sans will obey him, and vice versa.


  • Most ost names are related to death, pain or other bad/evil things.
  • The theme name 'World Dominator Gaster' is inspired by an ask on the True Geno Tumblr, in which Gaster jokingly answers his name means "World Destroyer Gaster".
  • The fact the test subjects have codenames is inspired by the UB codenames in Pokemon SM/USUM.
  • There may or may not gonna be a sub AU originating in the actual Underfell someday, which would be a true hell to live in.
  • It's not yet decided what exactly will replace the opera segment.