W. D. Gaster was the Royal Scientist before Alphys, responsible for creating the CORE and said to have disappeared. Gaster is a dark, and cruel entity scatteredW. D. Gaster was the Royal Scientist before Alphys, responsible for creating the CORE and said to have disappeared. Gaster is a dark, and cruel entity scattered across space and time. He is mysterious, and he likes to do science experiments to entertain him. He also likes creating Amalgamates, including one of Asriel Dreemurr's dead body.