The Detainer functioned as an Immobilizer 418 cruiser serving within the ranks of the Imperial Navy.
After the Galactic Empire's loss during the Battle of Endor, Lieutenant Lon Donell took control of the Detainer. He then engaged in acts of piracy, targeting shipping routes belonging to the New Republic. Operating out of the world Barpine, Donell used the Detainer as a base to grow his pirate forces through the capture of New Republic ships. Due to a shortage of available personnel, the Detainer was run with a minimal crew. Its complement included a squadron of TIE/LN starfighters, a pair of GAT-12 Skipray Blastboats, and also two Gamma-class assault shuttles.