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Underfail is an AU created by a Argentinian Youtuber called DeiGamer. Many of the characters are very stupid and act in a very silly manner (Except for Sans, Ink!Sans and Pandora (Chora)).


Frask falls into the underground, then they fall on top of bricks and meet Flawy. He gives the petals to Frask. Frask catches them, and instead of taking damage they grant HP. Then Tarial comes and accidentally steps on Flawy.

Eventually, Frask and Tarial pass through the trap with spikes, but Tarial does not remember where to go, and she dies in the arms of Frask. Tarial's SOUL appears and Chora awakens. They tell Frask to absorb the soul, but Frask mentions there is a small problem, and it turns out that they are on the thorns, and then they die. This story is repeated 300 years and uncountable stupid deaths without saving, much later Sans appears, and telekinetically moves Frask and Tarial over the spikes.

Later Sans asks Frask, "When it was your first time in the Ruins, did you commit genocide?!" Frask says they do not know what a genocide is. When they ask Tarial what it is, she replies, "Is it a cake?" Later, they argue that Frask does not remember anything after resets. Sans explains everything to Frask about Resets, and things, Sans responds that Frask having Chora inside them means Frask did Genocide, and their Frisk [ Maybe ] is very old, that everyone wants them to reset, but Frisk refused. Frask asked how Sans is still alive, Sans explain about everything, When Frask asks him how he got in their timeline, he explains he has an interdimensional machine, so he can travel anywhere. Sans wants everything to be Pacifist, and Frask argues that he is he taking too long. Sans has to explain about it, and about post-genocide. Frask thinks Sans is powerful, he explains his the weakest, Sans tells he have a special ability, but don't work on everybody, he tells Tarial to hit Frask, after, Sans uses his gaster blaster, Lowering Frask's Health point, into 1. Frask started to argue, Sans talks about Karmic Retribution, he says it only works on people who is full of sins, Frask started to be afraid, saying that they didn't do anything. Sans started to argue, until Tarial slapped Frask.

Sans started to shout at Tarial why did she slap them, Tarial says that she isn't the one who lowers Frask's health to one, Sans started to realize, Sans started to think about what Frask really is, After, Sans started to explain everything, and told Tarial about the symbol on her shirt, she responded that its like a premotion. Or its an Ornament, Sans tells Tarial that he doesn't know what does it mean. Tarial started to argue with Sans, saying that women have ornaments to look 'Beautiful'. Tarial started to say why she shouted, Sans says that the symbol on her shirt is affecting. Sans says that Frask needs to recover their memory, and be more intelligent, so they know what happened last time, Chora argues at Frask, but Frask didn't listen. Sans tells there is one way to Recover their memory and be more intelligent, he tells Alphys are having an experiment. To make Temmies more intelligent, until tragedies appeared, he can't get that image out of his head anyways, the only problem it was never used on humans. He think there will be secondary effects. After, He draws a Cross on the floor. He will look for it in his universe, He mention if he do it quickly, he has an opportunity to get to this moment. if he get the previous one, it would cause some anomalies. He doesn't want to explain everything to Frask again, If the Cross is still there, his very successful. He mention Frask and Tarial, both of them should wait, and don't screw with anything.

After, Tarial and Frask think they don't solve the puzzle, since they are on the other side, They forgot everything after Sans tell them everything. They do the same thing in the start. Meanwhile on Sans' universe, Ink started to appear, he tells sans not to go into any Aus, since it's his job to protect them. Sans argues with Ink, that his only Job is to stop Error and Nightmare. He tells ink only cares about the universe's temporal lines and every anomaly they suffer. Ink says that Genocide and Post-Genocide are not anomalies, they are misfortunes. they must not interfer them. Sans says that only handful of people deserve a happy ending. He 'screwed with the other aus, right? let everyone convert into dust' He tells its bad luck. He tells that Ink's mentality sucks.

When Sans returns to Underfail with the memory needle, he noticed Frask and Tarial weren't there and saw their dust in the spike puzzle, so he had to wait for them until they got back and explain everything all over again, and hoped that this time would be the last one. When Frask and Tarial finally came, Sans proceeded to explain everything again, and asked Frask if he was ready to recover his memory and intelligence

Frask asked if there was one way that the intelligence and memory were only temporary. Sans said he had tons of those temporary suerums but specified that he had to use the permanent one in Frask. When Sans finally injected the permanent suerum in Frask, the human started screaming in agony and pain, as he felt the past 300 years crawling through his back, begging Sans to return him as the way he was before, and finally conffesed that he made a Genocide Run and killed everyone. Sans asked why did he do it, but surprisingly, Frask said it wasn't his intention and started to explain everything

When Frask climbed to the mountain, he felt something strange happened as he accidentally inhaled the red smoke surrounding the mountain, and when he fell to the Underground, he wanted to befriend everyone, but he was unable to do it. Sans, very surprised, asked what was he saying, but then Frask answered that everytime he tried to act, spare and run away with every monster he encountere, they just suicided. Then, Frask said something evil started blooming inside him and started attacking everyone to see if there was a different result. However, the monsters just turned to dust after Frask killed them, and started killing everyone unwillibly, because something told him to do it. He then, sais that the last two monsters he killed were a king and a flower (Talking about Fail!Asgore and Flawy). And after that, he said "She" appeared, but before he continued talking, Frask shouted in pain and Fail!Chara was able to take control from Frask body. Sans asked her what has happende to Frask, but Fail!Chara said that Frask has died, leaving Sans in shock

Fail!Chara was finally free after 300 years being trapped as a ghost inside Frask, and also thanked Sans for that. Sans asked how was she able to take over Frask's body, but she asked hi instead "Are you able of controlling a hollow mind". Sans, shocked, understood that his attempts to fix that AU ended up by destroying it. Fail!Chara explained that she was able to revive when Frask completed the Genocide Run, saying that Frask was just crying and begging that the world would return to how it was before, so they made a covenant. Sans thought she asked for Frask's soul, saying that she was just as the other Charas, but he was worng, because, unlike the other Charas, Fail!Chara had her own soul and the things she needed were a body and something else (That "something else" is still unknown), but the bad part of the covenant was that she was unable to control or manipulate Frask, saying that his hollow mind was the thing that protected the entire universe, but it could've been resolver by absorbing Tarial's soul, because Tarial was a boss monster

Fail!Chara also said that, now that she's back, she doesn't need a boss monster's soul anymore, saying that her true self was finally awaken, but she was alarmed when Sans said Frask would get his memory back, although happy because he would also get back his intelligence. Sans wanted explanations because of what Fail!Chara said about "Getting back his intelligence", but she said Sans that she wanted him to call her by her real name, saying her real name was Chora. However, Sans started laughing a lot by the name her parents gave her, although she gave her a new name, thinking that when people heard it, they would be alarmed because the strongest person in the universe was coming, and sayed that when Sans injected the suerum to Frask, he opened Pandora's box, so he could call her like that (Pandora)

Sans then asked what was the second covenant Pandora made with Frask, but she just said that when Frask's brain started working completely, she was able to control it completely, and then said that after finishing the Post-Genocide run by doing the pacifist, but Sans asked how would she do that, bacause Frask said that it's impossible to do it because the monster were pretty weak, stupid and suicidal, but Pandora said she knew two things: The secret to complete the Pacifist Run and the monsters' hidden ability, called "Wild Instinct". When Pandora was alive, she was able to witness the Wild Instinct of a dog monster that was tormented by the humans everyday

When the dog monster used the wild instinct, he transformed into a giant wolf with horns and made a massacre in the whole city. Everything in that city was destroyed and no one was able to survive. Pandora also said that she knew the secret to make the monsters enter to their wild instinct easily

After that incident, all monster were sent to Mt Ebott, tricked by the humans because they lied saying that would be their new home. Although some monsters were able to know they were tricked and started hating humans to death. Pandora also revealed that the monster who destroyed that entire city was one of the weakest monsters, so Sans instantly knew that if all monsters entered in their wild instinct mode, the universe would be destroyed

Sans was now regretting of injecting Frask the permanent suerum, because even if he defeated Pandora and made her reset, Frask wouldn´t return, and knew that if he came back to the point where he was before, he would find his past self and said that this would make a destructive anomaly of such power that would destroy the entire multiverse. No matter what he does, Underfail was done for

Then, Pandora felt certain interest in Sans' machine, so she decided to kill Sans so he couldn't run away by using it. Sans asked her if she REALLY wanted to do a Pacifist Run, because he thought that killing him would just ruin it, but Pandora answered saying that killing him wouldn't ruin her Pacifist Run because Sans was from another universe. Sans was confident that Pandora wouldn't be able to kill him because of his speed, but... Pandora was millions of times faster than Sans thought she would be, because Pandora was already in front of Sans, and also saying the attack she made wasn't dodged, and that if she wanted to kill Sans in her first turn already, he would be reaaly done for. Sans was really shocked because he wasn't able to see Pandora's attack, and said that if she didn't fail on purpose, he would be already dead. Pandora then says that now it's Sans' turn, and told the skeleton he better not waste it

Pandora separates from Sans and tells the skeleton and that it was his turn to attack. Sans tries to attack Pandora by many ways, all of them proving to be almost useless due to her immense LV. In the end, Sans tries to create afterimages of himself to survive Pandora's slash, proving to be completely inefective. She says that it was fun to him, leaving the skeleton to death.



His name is often incorrectly said and his Friendship petals (Friendliness pellets) fill HP. He is very friendly.


Very forgetful when conducting Frask through the trap with spikes, and she forgets the way then dies. And then Frask dies.


Comes from another universe which ended in a True Pacifist. Helps Frask and Tarial pass the spike puzzle using telekinesis, recognizing that this timeline was the 1000th one.


A Very naive child. Climbed to the top of Mount Deigamer, thinking it was a good idea. They were manipulated by Pandora to do a genocide run


Pretty smart, evil and seems to be one of the strongest characters in Underfail, probably losing only to the Demon. She wears clothes similar to Chara's, but with black and red stripes. Her face is completely demonical, with the eyes being completely red with black pupils and the mouth being permanently into an unatural size, without teeths and blood dripping on it. Could have killed Sans at the very start if she wanted to. It once had her soul shattered in many pieces, weakning her powers greatly. She prefers to be called "Pandora", because of all disasters she caused and by hating her true name. Has be shown to be able to destroy AU's with a single swing with her knife. It's powers include, but are not limited to:

-Super Speed

-Strings (similar to Error's)

-AU jump (it once had this power)

-Knife Slash (by swinging her knife, she's able to use high amounts of energy into destructive power.

-Power Reflection (as was shown to reflect the blue magic)

-Mind Manipulation


-LV absorbtion (the ability to turn LV into raw power. Eventually, it will change forever the physical appearence of the user)

-Timeline manipulation

Mysterious Demon

A mysterious character, responsible to be the one who gave Pandora her powers. It's heavily implied to be stronger than Pandora. Theorized to be the Devil. It haves a giant humanoid appearence, with red skin and black horns/nails. It's eyes have are yellowish slit, like those of a snake. It wears only one piece of cloth, exposing his bare chest.



  • This AU was created by a Argentinian youtuber, DeiGamer.
  • After a while, the AU started to be published in color. Each character`s color scheme is based in DeiGamer`s research and interpretation of colors.
  • Unlike Toby Fox, DeiGamer decided to give a gender to Frisk and Chara, being Frisk male and Chara female.[citation needed]