Sans is a fictional character created by Toby Fox for the 2015 role-playing video game Undertale. Initially appearing as a friendly NPC with an easy-going and laid-back personality he becomes the de facto final boss if the player chooses to complete the "genocide route" and go out of their way to destroy the game's race of monsters.
His name is based on the Comic Sans font, which is used for most of his in-game dialogue.
. . .
