The Controller of Planet X, also known as "The Controller" or "X" for short, is the supreme leader of The Planet X as his name implies. Initially bent on destruction, X changed his ways after a brush with death, when a giant three-headed serpent dragon destroyed his city, killing most of his family. Forced to move underground, X was determined to keep the dragon, King Ghidorah, at bay, and also protect the cosmos from Ghidorah's vicious wrath.

X was born in an incubation chamber, which is the norm for all Xilians. His parents were of noble heritage, so it was presumed that X would likely find himself in a position of power, perhaps even as The Controller himself. After excelling in his studies, X was appointed the youngest intergalactic space battalion commander at only 18. After years of conquest, then the subsequent destruction of his home city by the wrath of King Ghidorah, X joined forces with Boot heel to subdue King Ghidorah and keep the cosmos protected as well.