Dr. Wing Din Gaster was a member of The Wizard Council before the events of the Human-Monster War, in which the monsters were sealed beneath Mount Ebott. Wanting to free the Monsters from their imprisonment, the royal scientist focused on soul experimentation, which eventually led to him falling into The Void. For an indefinite amount of time, he remained trapped in limbo, forced to watch every timeline simultaneously. He is eventually rescued by Sans, one of his two children.
Appearance
Gaster is a male Boss Monster that has a skeleton-like appearance. His two eye sockets have permanent scars coming from them. Gaster typically wears a large black coat over a lighter shirt, with brown pants and shoes. He sometimes wears a white lab coat when performing experiments inside his lab.
When triggering magic, his eye color depends on the status of his two children. When Sans and Papyrus are alive, he'll have both a red and light blue eye. If one were to die, that corresponding color will fade away. If both were to die, his eye color will return to its original purple.
