Wizards of Ertshea

At some point before squaring off against P.R.O.B.E., the Greth attempted to invade Ertshea, later claiming the title of "Scourge of the Wizards of Ertshea". (PROSE: Out of the Box)

Behind the scenes

The name of Ertshea is reminiscent of Earthsea, the setting of Ursula Le Guin's highly influential book series of the same name, the first book of which was entitled A Wizard of Earthsea.