Gaster tried his hardest to stop the human, but no matter what he tried it was to no avail. Gaster would encounter the human multiple times however, his second encounter would leave him wounded until he is saved by Sans. Sans and Alphys becomes co-workers for Gaster helping him create new devices and machines to help monster kind to prepare for human attacks and to harden the monsters' minds in the Underground so that they won't be manipulated so easily.Įventually the seventh human arrives and once Gaster sees him in the monitoring station he ambushes him, but he is unsuccessful in capturing the human's soul. Gaster announces to the public that the sixth human is the cause of the civil war and proposed to focus all their efforts on recruiting more monsters into the Royal Guard which the majority of the Underground agrees with him. After the chaos ended Gaster investigates the cause of the war and finds that the sixth human setup the war to his surprised horror. Years later once the sixth human falls down the Underground after Chara, a civil war started and he becomes the head operator in communications and using his teleportation ability to help monsters who need medical attention no matter what side they were on. Gaster mourns their deaths after their encounters with Asgore, but believes that it is for the greater good so that monsters may see the sun again. Gaster at one point becomes friends with the humans Emerald and Aqua for their positive contributions for the Underground. Gaster eventually becomes the Royal Scientist creating the Determination Extractor, The Core, and creating many other systems throughout the Underground. Before Gaster becomes the Royal Scientist and in his younger years he helps the Mountain King put the human souls into the containers while also comforting Asgore encouraging him to keep going in difficult times.
Gaster is the Royal Scientist of the Underground alongside his co-workers Sans and Alphys and he currently helps the Mountain King escape the Underground using various other methods while also finding new discoveries to help his people.