Gyiyg

Known as both the "Embodiment of Evil" and the "Universal Cosmic Destroyer", Giygas is an evil alien who, upon failing his original mission to reclaim the knowledge of PSI from humans, intends to sentence all of reality to the horror of infinite darkness. With an army of Starmen, Octobots and other deadly war machines, Giygas also uses his immense power to influence certain Earthlings to assist him, such as Pokey Minch and Geldegarde Monotoli. His influence also causes animals and people to become violent and distressed. He belongs to a race of aliens who originally had the power of PSI and, for unknown reasons, abducted humans in the 1900s and 198X.

(Source: EarthBound Wiki)