Sans once lived within an AU known as AdditionalTale, Which is much like Undertale execpt Gaster was never thrown into the core and Sans and Papyrus have a little sister named Serif. Sans lived for many years, Then something happened, a human fell into the underground. They began a path of genocide and killed everyone. This fractured the code and threw Sans into the anti-void, he quickly realized that he could use his magic to travel throughout the multiverse without disrupting the code. From then onward he made it his mission to capture and contain every wielder of Determination within the Anti-Void where they could never go on a genocidal rampage
Containment!Sans is much like an ordinary sans, though he sports a black leather coat and a bandage over his left eye socket.
He has -1 hp and cannot be killed by normal attacks , only by using healing magic can he be defeated. He was stabbed in the eye by the human, meaning that he cannot manipulate gravity or use gaster-blasters, only bones and blue attacks
He is not very well known so he hasn't encountered many of the other out-of-code characters.