Originally, Greyscale Sans heard about an outbreak of a virus that made the monsters infected with it lost their soul and body color, which caused them to go crazy and kill their loved ones. Soon after, Sans was infected with the virus, and his body and soul color changed. Sans went crazy and killed everyone he knew and loved including Papyrus. His original soul tried to fight back, but it was no use. After the last human fell down, Sans kept hiding in the bushes while watching them. When the human passed by, Sans would leap out at them and kill them. Later, a very tragic story happened. Error deleted Grayscale's universe leaving only Grayscale to remember it, which soon caused Grayscale to rip off half of his soul to create Papyrus again. But this Papyrus was demented, and kept trying his best to kill Sans. Unlike Classic Papyrus, Grayscale Papyrus does not care for his brother, even if he is dying.
Grayscale wears a dark grey hoodie which is covered in blood and dust. His left eye glows red while tears fill up his right eye. His skull is cracked open, and light grey particles surround it. When Error deleted his universe, white or light gray glitches surrounded him.
Bones: Standard attack
Gaster Blasters: Standard attack
Ghosts: Using this power, he can summon previously infected ghosts which are forced to obey Grayscale.
More HP: Since he has killed monsters, he has more HP than most Sanses (He is at LV 9999)
Grayscale Virus: If he has enough energy, he can infect YOU with the virus temporarily.
Cloning: He can make copies of himself, but the maximum is only 2.
Timeline-Jumping: He can move from timeline to timeline, infecting others with the virus as well.
-His glitches can cover his face up, making it impossible to see, which also makes it easy to land an attack on him.
-The grayscale virus can sometimes deactivate, but other people do not realise that he is the actual Sans, which can kill him permanently. this has never happened though
-Even though he is almost impossible to kill, resets DO bring him back to LV 1 and the monsters he has killed do not come back. After he has killed everyone in the multiverse and a reset happens, he will not be able to become any stronger than LV 1.
-He has a habit of making himself freeze, which makes it easy to inflict major damage on him.