Therbon held the rank of Moff within the Galactic Empire during the initial years following its establishment. The Imperial ambassador stationed on the planet of Murkhana repeatedly requested reinforcements of stormtroopers from the Moff to combat local criminal activity; however, the Moff did not dispatch any troops. Subsequently, during a visit to Murkhana by the Sith Lord Darth Vader and Imperial Governor Wilhuff Tarkin in 14 BBY to look into a suspected rebel cell, the ambassador voiced her grievances regarding the Moff's lack of action.
In 2012, The Essential Guide to Warfare, a Star Wars Legends sourcebook authored by Jason Fry and Paul R. Urquhart, first mentioned Therbon as a Grand Moff. Later, the James Luceno novel Tarkin, which was released in 2014, introduced the character into canon. Neither source provided details about Therbon's gender or species.