Backstory: The Sans' were tired of fighting people in this world and in AU worlds, so, he decided to have a meeting with all sans' and they gave normal sans and his ghaster blaster a lot of powers, Papyrus decided to join, because the player did genocide route, only his head and glove was left, so he turned evil and the group hated humans, now no human would dare to visit the mountain, the humans were not curious at all because they knew what would happen if they went inside the mountain
I just created what it would look like if sans was too tired of humans and what it would look like if he had a final final phase(he somehow heals his wounds and becomes so strong that he could destroy the whole universe if he wanted to)