The Onager-class Testbed served as an experimental platform in the development of the Onager-class Star Destroyer. This starship featured a distinctive bow, characterized by a central indentation flanked by two projecting prongs. Located within each prong was a hangar oriented towards the rear of the vessel. On both the port and starboard sides of the central indentation, an Orbital Bombardment Particle Cannon could be mounted, enabling the ship to strike celestial bodies from outer space with its projectiles. Furthermore, the ventral surface of the ship incorporated stepped sections and a central dome situated behind the particle cannons.
A vessel of this testbed class was part of the navy under the control of the Galactic Empire. This particular ship was outfitted with a pair of Orbital Bombardment Particle Cannons, both of which were deployed to bombard a brown planet from space. The Onager-class Testbed was not considered as versatile of a capital ship when contrasted with the finalized Onager-class Star Destroyer, which the Empire eventually put into service.
The Onager-class Testbed made its initial visual appearance, though without a specific designation, in "A New Age of Battle," an article from Fantasy Flight Games promoting the Star Wars: Armada miniatures game on their website, dated August 1, 2019. The name was later revealed in the article "The Siege Breaker," also published by Fantasy Flight Games for Star Wars: Armada, on November 25, 2019. The ship's design was originally conceived for a card of the same title included in the Onager-class Star Destroyer Expansion Pack.
- A New Age of Battle on Fantasy Flight Games' official website (backup link) (First pictured)
- The Siege Breaker on Fantasy Flight Games' official website (backup link) (First identified as Onager-class Testbed)
- Star Wars: Armada — Onager-class Star Destroyer Expansion Pack (Card: Onager-class Testbed)