I finally found the original post, pops!
This is a long ass post so feel free to hate me if you don't like it
My AU is called Mastertale.
During a genocide run, Chara is fighting Sans to get to Asgore, but they fail and die. They Reset and fight again, and they die. Over, and over and over. Eventually, they start resetting the entire Underground, killing every monster again and again and again to try and maximize their power, and every time, Sans has to watch everyone he cares about get killed in a seemingly endless loop for a human child's boredom.
Even with all the Resets, Chara still couldn't manage to beat Sans, and soon their soul shattered... and didn't come back
Sans sat in the judgement hall, waiting and waiting. Nothing. They weren't coming back. They weren't going to Reset.
Filled with the grief of losing everyone he ever cared about, Sans was Determined to never let anything like this happen again.
He took half of the soul on the ground and fused it with his own, filling him with Determination. He gained the Power to Reset. He Reset the entire Underground, bringing all the monsters back. And since the human quit, Sans was able to protect the Underground for many years.
Unknown to Sans, Flowey took the other half of the soul of Determination and tried to absorb it with the other souls that Asgore had collected. However, the broken soul disrupted the process and set all of them free, wandering the Underground in search of Sans, who had absorbed Frisk's half of the soul. Meanwhile, Chara's soul came alive again, and searched endlessly for another human so they could have a body again and finish what they started.
Once upon a time, there was a human boy named Felix. Felix was on his way home from school when he saw half of a glowing red heart floating in the distance. Overcome by curiosity, he followed it. It led him to the top of Mt. Ebbot, and disappeared down a giant pit. Felix walked closer to see where it went, but tripped on a vine, falling down into the Underground.
The heart piece that Felix was following was Chara's half of the Determination soul, and finally having a body to manipulate, they joined Felix's own soul in his body while he was unconscious on a pile of glowing yellow flowers.
The other souls that had been accidentally freed by Flowey saw what Chara was doing. Not wanting to let them attempt another genocide, they also entered Felix, unknowingly granting him great power.
When Felix wakes up, they explain to Felix what happened, where he is, and how he can get back home. However, they all wanted to save Frisk from Sans. See, Sans doesn't know that Frisk was a pacifist, so whenever they tried to communicate with him, he panicked and suppressed them, causing them a lot of pain. The other human souls wanted to help Frisk so they wouldn't have to suffer anymore, and Chara wanted Frisk's soul half back so that they could have their own body back to commit another genocide.
The good souls can appear around Felix in ghostly forms to give him advice and just to talk. Chara only has half a soul, so they can only speak to Felix through his own mouth, turning half of his face into half of Chara's face.
All the souls wanted to influence Felix in some way to do what they think is right, but Felix has his own trait. His unbreakable Will is what would get him through whatever came at him in the Underground.
His Will gives him three new buttons, rather than Reset.
Backup - Felix can save the data of anything to be brought back later exactly in the state that it was backed up in. He can use it on himself, on other monsters, on objects... maybe even the whole Underground.
Restore - Basically what makes Backup useful. It restores the backed up data
Mod - The god button. He can alter anything in any way. Objects, monsters, himself, memories, the timeline, anything. But it only works if his Will is strong enough.
With the souls inside him and the three buttons' power, Felix can be whatever he wants to be in this world, ready to fight a Sans who's long ago given up on humans.
Fun details! - Flowey gave up on trying to destroy the Underground
Toriel opened up a school, and has convinced most monsters that humans aren't simply evil in nature
Papyrus - Now the captain of the royal guard, which has become more of a search and rescue force. He's not as obsessed with humans anymore and helps Felix throughout his journey
Undyne - Settled down with Alphys and left the royal guard to Papyrus
Alphys - Settled down with Undyne and focused her research on improving Mettaton. She also made her own anime
Mettaton - He has his own successful talk show. The ratings have gone through the roof
Muffet - Her bakery has become famous with her new menu item: Spider Muffins. Her pet spider had babies
Monster Kid (Now Monster Teen) - They train to be a royal guard under Papyrus. Obviously they're a little older now.
Onionsan and Shyren - They make music for Alphys's anime
Dogamy and Dogaressa - They retired and have twenty puppies
Woshua - Opened a dry cleaning business
Mad Dummy - He's a therapist
River Person - Still the same dude
Asgore - Takes care of Flowey
Sans - The new protector of the Underground. He hates any topic involving humans and thinks they all deserve to burn in hell. He gets mad at Papyrus for helping Felix.
Thanks for finding this, Felix! There's some other stuff I came up with since this was first posted, so...
(New stuff)
Master Gaster - Not exactly a villain. With the Chara gone, he had no experiment and decided to make a successor. For funsies I gave him Overwrite from Xtale (by Jakei)
Z-Serif - Master Gaster's new creation. Capabilities unknown.
I hope it was easier for you to read than it was for me to type.
This is Mastertale














