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Wing Din Gaster is the Royal Scientist of the Monster Kingdom of the Underground. He was created by the Royal Scientist before him, S. Keletonn.
Wing Din Gaster is a very tall skeleton with two vertical cracks/scars on his skull: one going from the top of his right eye upward, and one going from the bottom of his left eye down to his mouth. He has white pupils that dilate when he's angry and turn purple when he uses magical psychokinesis. He wears a light, black coat that goes down to his feet, which gives him the appearance of gliding, and a scarf to protect his sternum. Nothing is known of what he wears underneath the coat. He wears gloves bearing black circles with white designs on the backs.
Gaster is very professional, always speaking with proper grammar, the exception being when he's angry. His professional tone stems mostly from his former and current occupation of Royal Scientist. His tone towards others reveals that he is also somewhat apathetic. After being shattered across time and space, he gained the ability to retain his memories through RESETs, which allows him to be someone that Friskara feels she can talk to when she's having a crisis. His overall appearance and voice cause him to be intimidating.
Though Gaster is somewhat intimidating and manipulative, he actually has a soft side for children and the infirm. He is also very observant; he can read others' faces, and is often asked by the Royal Guard to help out with major cases. He hates bad puns, but chooses to put up with them for the sake of keeping his assistant, Sans. He enjoys science fiction and secretly goes to a blood bank on the surface every weekend.
His favorite television show is RWBY, though he would never admit it.
Gaster can quickly travel or teleport using Sans' "shortcuts."
In combat, Gaster uses "Gaster Blasters" to shoot a kind of laser beam. Gaster excels in combat and fights similarly to Sans, the exceptions being his attacks doing 15 damage and his Karmic Retaliation dealing damage proportionate to his opponent's LV. Because of his research, he is able to use all types of magic attacks, including red attacks, which toggle his Karmic Retaliation.
Gaster agrees to help Friskara and Flowey and even gives Flowey an artificial SOUL.
Gaster reveals that the artificial SOUL given to Flowey, which transformed him into Azzy, was in fact his own. He then goes to great lengths to monologue his origin story. Soon after he finishes his monologue, he is stopped from taking control of Azzy's body by Azzy. He later agrees to a proposition made by Sans.
Sans separates Gaster from Azzy, and he goes with everyone to Asgore to give him the news of the presence of Azzy, Friskara, and himself, Gaster.
He is present in the throne room when Sans briefs Asgore on the news, and agrees with everyone else that Jerry is evil.
He is present during the get-together that Friskara arranges with Asgore.
He thinks of Friskara as a pseudo-daughter.