"Do you Wanna Have A Helluva Time?"
– UnderHell Sans



Once upon a time, Sans was born alone with no one. There was no Papyrus, no Gaster and no Toriel to comfort him so naturally, he became a bad guy until one day while he was wondering around Deadin (Snowdin) and he came across a blue string. He followed it as it had peaked his curiosity. So he followed and as he did he found more and more strings. Eventually, he found another skeleton. For a moment Sans thought he found a new friend or just maybe a new family member. However, he quickly realized that was no ordinary skeleton. This skeleton was completely black. He was covered from the skull down with error signs and the blue strings were emanating from him. Sans took a step back, but his foot landed on a stick and it snapped alerting the skeleton to his presence. The other skeleton smiled and said, "Oh and here I thought there wasn't another Sans around here, but hey makes my job a whole lot easier." The other skeleton attacked Sans, but luckily he was able to dodge. However, right when Sans was about to attack back the blue strings latched onto him like glue. He tried and tried to get them off, but they were on him so tight he might as well have been trying to lift a cinder block. The strange skeleton approached him and told him ''Don't worry this isn't personal, it's just businesses.'' Sans quickly began to feel his life drain away. He saw someone come out of wet paint from the side of a house. It was another skeleton. Except this one was holding a giant paint brush and had strange eyes. As the new skeleton yelled out ''ERROR!" Sans quickly took his opportunity and fired a Gaster blaster at the black skeleton. However, the skeleton noticed right away and dodged but in the process setting Sans free. As Sans fell to the ground his skull began to hurt. He watched as the two skeletons fought he was wondering ''WHAT THE HELL IS GOING ON HERE?!". He quickly teleported away from the scene. A few days later Sans had just finished leading the human through Lavafall and after he had explained to Undyne what the human was trying to do she let them pass on through. Sans said goodbye to the human at ColdValley. After that, he teleported to his favorite spot right at the edge of Lavafall's biggest lavafall, The Great End. It was this huge lavafall that was said to lead to the core of the planet, but of course Sans didn't believe that, but myths aside Sans began to feel his head hurt again. He thought turning on his purple eye would help, but instead, he got an even worse result. As soon as he opened his eyes he began to see strange things like another world where there was another him, another Undyne, and another skeleton called Papyrus. He also saw a man called W.D.Gaster and a kid named Frisk and Toriel wasn't a ghost and... "...I.....Understand.....Everything...Now." he said. Once he finally got himself together he started to build a machine. A machine that would take him somewhere where everything is okay, where everything is right

Fun Facts

  • UnderHell Sans is the laziest of all the AU's
  •  UnderHell Sans's Lv is 23
  • UnderHell Sans loves to eat pie

figure out why by checking out my other post but if you don't know why it's because he (unlike the other Sanses) works but not the way you think. His job involves killing other monsters that he finds unreliable. I thought I should also talk about Sans's Red eye. So Sans in Underhell as you've seen isn't very nice. His appearance can tell you that, but that's not all. Sans in Underhell is the main reason why there's a low population of monsters in the Underground. He also has a reputation for being incredibly powerful. This tends to go to his head. Because of this one day he sought out more power. He did this so that he could control his timeline. The reason why he wanted to control the timeline is so that he could possibly be able to reset or just get stronger. So on his quest for more power, he went to the True Lab while Alphys was out taking notes on Flowey. Sans took some Determination and used that to make him unpredictably strong. It worked but with unexpected consequences. He immediately began to melt and deform around his ribs and chest region. Eventually, it dialed down and the melting stopped. He eventually was able to get back on his feet and had Undyne make him a new jacket. However, she had run out of blue string so Sans would have to deal with the blood stained jacket he already had from when he killed half the population and from his accident with the black skeleton. So that's why he has a red jacket and a red eye.


Timeline Jump: since his encounter with error! sans underhell sans has got some new abilities such powers as Timeline Jump a power he can use to jump from a genocide path to a neutral or a pacifist.

Gaster Blaster: 10 damage

Bones: 2 damage

Determination: since underhell sans has the power to reset and load like frisk can in undertale.

More Hp: and Since He has determination like Dusttale sans underhell sans can take more than one hit.

Au Jumping:Error when he retreated to the anti-void left his portal open which means underhell can enter t.he anti-void.

Burning Bones: deal damage 1

Burning Blaster: deal damage 9

Hacking UnderHell

  • Do you know if you cheat in Underhell your LV will drop to

-20, your hp will be -20, and you will automatically be put in the Sans fight. So I ask you "Are you ready to have a Helluva time you dirty Hacker?".

Feminism vs Mannerism

  • Unlike Undertale Sans UnderHell Sans copes by turning his eyes off.

To make him look more like a real skeleton. Also if you guys didn't know in UnderHell most characters don't show their eyes just like how Sans does because in this AU it magic is used to look good. Women don't do it because it's unladylike. For men, it doesn't really matter and Sans does to look scary which is all the time.

Judgement Dome Fight

  • In my UnderHell fight when you first beat Sans it will

actually take more than one hit to kill him because the first strike actually hits a ketchup bottle he brought with him just in case he failed. Also when he gets hit he strikes you with a gaster blaster killing you because you have 1Hp and then he leaves the judgment hall making you have to wonder around to find him again. UnderHell Sans doesn't believe in Sparing or Mercy. If he catches you sparing someone his opinion of you will change. If you kill someone or chose to do a Genocide route he will call you worthy or someone of interest. He will start to watch you as you kill everyone. Eventually, on some occasions, he'll even try to fight you. BUT DON'T FORGET WHERE THE TRUE BATTLE BEGINS!

Timeline Jumping explained

  • In UnderHell Sans has the ability to travel between different

timelines so if he isn't happy with what your choices are (sparring and using mercy) he could go to a completely different timeline. Example: If you were doing a Pacifist run he could just decide to not to be around all the sweet and nice feels so he would go to a genocide run timeline. In other words, he would go somewhere that (in his opinion) is more exciting.

Love Interest

  • Did you know Sans and Undyne in this AU are in love each other

but their Pride and Ego's are so big that they are too shy to confess?


Acts very serious and doesn't take everything with a gran of salt. he enjoys making puns more than any other Au. he doesn't enjoy being around people who don't do their job,but in the end ends up slacking off himself.


  • Toriel - Ghost
  • Asgore- Dead
  • Alphys - Dead
  • Undyne - Alive
  • Gaster - Unknown
  • Brisk and Vara - Alive
  • Toby Fox - Alive
  • Dusttale - On Shit List
  • Underfell - Frenimie
  • Mac-au traveler,Possible friend


You can add something as long as it's not negative

UnderHell Sans hates Dusttale sans and Killer!Sans

UnderHell Sans is stronger than Dusttale Sans, but is not sure if he can beat Killer!Sans since they haven't fought.

once underhell sans goes to sleep he stays asleep for 48 hours.

UnderHell Sans is The strongest Sans, this is possible because of his Lv and the uniqueness of his AU

UnderHell Sans has never thought of raising his Lv anymore then it already is Because he feels that if he did he would turn into a psycho path like Dust and killer!Sans

UnderHell Sans is the best sans at dodging

UnderHell Sans has denied ever Request and ever chance to be on Nightmare!Sans's team


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