In the mirror universe, Ardana was a planet in the Mu Leonis A system in the Beta Quadrant. It was the homeworld to the humanoid Ardanan race. It was a subject world of the Terran Empire during the 23rd century and of the Klingon-Cardassian Alliance during the 24th century.
In 2277, Plasus was the Governor of Ardana. That year, he was one of the many witnesses of Empress Hoshi Sato III's disintegration using the Tantalus field and the immediate proclamation of Grand Admiral Spock of the Imperial Starfleet as Emperor. (TOS - Mirror Universe novel: The Sorrows of Empire)
In 2295, Ardana was conquered by the Alliance following the fall of the Terran Republic, the successor state of the Terran Empire. By 2371, the half-Klingon, half-Terran B'Elanna was the Intendant of the planet. (VOY - Mirror Universe novel: The Mirror-Scaled Serpent)