Gaster has transformed into a large, disfigured skeleton monster with a fractured Gaster Blaster for a head and has a purple substance dripping down his mouth. He is the former Royal Scientist who was erased from existence after an unknown accident. After hundreds of Genocide Runs caused by Chara and the player, Gaster was eventually released from the void by Sans, who had been killing other monsters to stop the madness, not knowing that he was still trapped in a loop.