Doonium was a metal that was used primarily for starship construction. Doonium was found on numerous planets around the galaxy which the Empire mined. One particular planet this material was found on was Lothal.
Three people in particular, Thrawn, Eli Vanto and Nightswan all noticed that Doonium was being transferred to an unknown point in the galaxy, though only Nightswan himself was trying to stop shipments of Doonium from being sent to whatever the Empire was creating.
Thrawn later learned from unguarded dispatches that the Doonium was being sent to the Death Star.
- Thrawn (First appearance)