The Mule establishes his empire incrementally, using past conquests to aid new ones: first by mentally converting a pirate band to his allegiance, then a whole planet, then the militarily powerful kingdom of Kalgan, which he obtains by mentally converting the warlord of the planet, and then defeats the Foundation. The Mule sets up his own short-lived Galactic Empire, the "Union of Worlds", styling himself "First Citizen of the Union" and making Kalgan its capital planet. By design, almost no one ever actually sees the Mule or knows what he looks like until a good time after the Mule's conquest of the Foundation and its trade confederacy.