Gaster was the creator of the CORE, geothermal energy converter. Later in his life, while trying to find an alternative way to escape the Underground, he started to research the void, this started by researching Sans’s ability to teleport, and expand on it, seeing as he used the void to pass through from one place to the other... Only to find that Sans is still limited to the mountain and cant leave, even through that way. So they start to research and build a machine.... Only for something to happen and Gaster, ‘FELL’ Into the machine - getting sucked into the VOID and being erased from existence.
Before this happened, Gaster pushed his oldest son out way, saving him, but not enough, for he was knocked back and he was caught in the blast. This would then give him the ability to remember Gaster and the RESETS.
Sans of course worked hard as the Years went buy, took his younger brother, Moved to Snowdin, and continued to work on the machine, but it refused to work.... until the barrier broke and they all moved & settled on the surface...
Ebbot city wasnt big nor was it small, but after half a year of talking, the deeds to the forests and land around the mountain, and the mountain itself (And Ebbot Town) was granted to the Monsters, And Ebott City was names the Monster capital.
There were still those who decided to stay living in the mountain, while there were also those who wanted to only live in the City that was being newly built at the Base of Mt. Ebbot...
Sans started to once again work as a scientist, being one of only two people who understood the CORE. But in his spare time he continued on the machine - One day... it just started to finally work, Freeing Gaster and returning his existence and memory to the world. He was given his original position, freeing up Alphis and letting her have more free time with Undyne and other friends.
Papyrus is also the mascot for Monster Kind, greeting everyone with a smile.
