The Z-X3 experimental droid trooper, a battle droid prototype, was developed by the Tagge Company during the Galactic Civil War period. These droids were conceived for operations in environments too dangerous for biological stormtroopers. The Z-X3's creation was spearheaded by Imperial officer Rom Mohc, who drew inspiration from his prior encounters with Confederate battle droids during the Clone Wars. Despite their potential, the Empire ultimately rejected the droid troopers, resulting in the few produced Z-X3 units ending up in either obscure Imperial assignments or private ownership.
Serving as essentially the second iteration of Tagge Company's L8-L9 battle droid design, the Z-X3 experimental droid trooper was engineered for deployment in harsh conditions deemed unsuitable for the Galactic Empire's organic stormtroopers—notably, highly irradiated or zero-G zones. Standing at a height of 1.9 meters and possessing a humanoid form, the Z-X3 droids were aesthetically designed to resemble the stormtroopers they were intended to augment, featuring crimson plating inspired by stormtrooper armor. Lacking integrated weaponry, the Z-X3 commonly utilized a blaster rifle or a Briletto AAP-IV blaster box mounted on its chest. Furthermore, these droids possessed enhanced physical capabilities and a sophisticated level of intelligence independent of a centralized computer network.
The Z-X3 droid trooper, a product of Tagge Company's creation and manufacturing during the Galactic Civil War era, originated from an idea conceived by Imperial officer Rom Mohc. Mohc, having served in the Grand Army of the Republic during the Clone Wars, developed an admiration for the Separatist droid armies. Consequently, Mohc became deeply invested in the concept of droid stormtroopers capable of providing support to the Empire's organic ground forces. To realize his vision, Mohc initiated the "Droid Trooper Project," and in the years following the Battle of Yavin, he secured a willing collaborator in the Tagge Company. Its Baron, Orman Tagge, remained keen on the idea following the unsuccessful deployment of his L8-L9 droid model during the Clone Wars.
Initially, TaggeCo produced a limited batch of fewer than 100 Z-X3 units, sufficient for the Empire to conduct testing in a controlled environment. However, the memory of the Separatist battle droids' defeat was still prominent in the minds of the Imperial leadership, leading to the project's termination. Although Mohc would later refine his concept into the Dark Trooper Project, the few Z-X3 droids were rejected and earmarked for decommissioning. Despite this, some found service with the Empire in remote garrisons, while a larger number ended up in private hands. One such droid, later known simply as Z-X3, made its way to the "Droid World" of Kligson's Moon, where it became the chief lieutenant of the cyborg technician Kligson while secretly harboring Imperial loyalties. In 3 ABY, Z-X3 instigated a rebellion with the aim of seizing the Droid World in the name of the Empire, but it was ultimately defeated and destroyed.
The Z-X3 experimental droid trooper made its debut appearance in Star Wars (1977) 47, penned by Archie Goodwin and published in 1981. The droid class subsequently received a comprehensive backstory, along with its full designation, through an entry in The New Essential Guide to Droids in 2006.