UnderBlank AU InfoFirst off, UnderBlank is an AU based off of the game, Undertale by Toby Fox: http://undertale.com/
Please, if you haven't played the game yet, I urge you to do so, and that you do not read my UnderBlank AU comic because it will contain spoilers!!!
Background on UnderBlank AU:
it's based on the assumption that the first time you play the game, Undertale, it's not your first.
Somehow, Sans is aware that the human affects timelines--I know there might an argument that Flowey could have also been some type of warning to Sans but then how did Sans know in particular that the human was the one who affected the timelines the most?
thus this AU is basically a story about the first time Frisk falls down, unaware of what is about to come, and how Sans became to know that Frisk has the potential to destroy his timeline over and over.
So basically UnderBlank Sans is unaware of resets, hence his magi