essentially his lore is

He was a fun value event created by a glitch in tobys code where you could have 2 fun values set at the same time.

if he was encountered,he would replace sans throughout the entire game and would say no dialouge.

If you did the genocide route he would have a custom made battle with the garbage noise from Deltarune as the background music. His Attacks Were random sprites ripped from the spritesheets. Noteable ones are undynes walking animation,Snowdrakes battle sprite,Various ui elements and Asgores throne. The battle would be nearly impossible to beat and the only way you could was if you used cheats.

when you kill him,He would Just stand there staring at you. Until after a couple minutes he would say the line “don’t you recognise me” and the game would crash.

toby had patched this in a update,leaving him stranded in his world. Since he was the only character in it,he made it his domain and could do anything with it. He saw how the actual game was in a later update,and started forging the world from there. sadly there were no remnants of the characters and Despite how many times he tried he could not get anything working,sitting there alone,for eternity.