There is a special existence among many AUs, what is it called? _TALE is the parallel universe version of UNDERTALE.
In this world, timelines are separated by magic. But there isn't that much magic under the ground that can be used to support these different timelines. Then? _Gaster invented the core and added another of his inventions to it - a device that can convert the core's thermal energy into magical energy, bringing blessings to many monsters underground.
? _After Frisk cleared the line of hypocrisy, all the monsters in the underground went to the surface to start a new life. The core system had some failures because it had not been repaired for a long time. ? _When Sans took a shortcut, time and space slowly became distorted and confusing, and he came to the massacre line that Kamijou had already cleared.
In the process of fighting with his "friends", the distortion of time and space caused various memories of this timeline to appear in his mind, as well as the scenes when friends and relatives were killed one by one, but he was unable to recover. Exist? _Chara with? _Under Frisk's strong determination, Sans was defeated. Just when he was about to turn into dust, time and space were disrupted again and he was sent back to the original timeline. But it still couldn't slow down his death. He lay beside the tree panting and covering his wound... At this time, someone hurriedly walked towards him.
(It's a self-created AU, called Lost Legends, and Sans is called Mist! Sans. I hope there is no similarity qwq. It's the first time I write something like this, emmmm... The writing is not good, please forgive me. I humbly ask you to click to collect it! QwQ These will become the motivation for my creation! Due to some reasons, updates are often delayed, but this article is completely exempt.)
Intention: Fog! The origin of sans.