Doonium, a substantial metal, played a key role in the building of starships. This material was mined from various locations across the galaxy, including numerous planets and asteroid fields. Specifically, Batonn, Umbara, Samovar, Lothal, and the Socorro asteroid belts were sources of doonium. Pryce Mining initially managed the Lothal doonium mine; however, Arihnda Pryce struck a deal with Senator Domus Renking, which resulted in the Galactic Empire taking control. Mark One Pistoeka sabotage droids were among the technologies that utilized doonium.
Following the conclusion of the Clone Wars, the Empire engaged in extensive doonium mining and stockpiling. This was done in secret to facilitate the construction of the Death Star superweapon. Doonium, along with dolovite, proved vital for shielding the hypermatter reactor core and focusing dish. During the time, Thrawn, Eli Vanto, and Nevil Cygni each observed the movement of doonium to a clandestine location within the galaxy. Cygni, operating as the rebel agent "Nightswan," actively fought to disrupt the Empire's doonium shipments, driven by fears regarding the Empire's clandestine project. Thrawn eventually discovered the true purpose of the doonium through intercepted, unsecured communications.