The AT-DP Arc Cannon Prototype was a prototype Imperial walker that contained the Duchess, an arc generator designed by Sabine Wren when she was still a cadet at the Imperial Academy on Mandalore. It was named after the late Duchess Satine Kryze, who ruled the New Mandalorians during the Clone Wars.
The AT-DP Arc Cannon Prototype was based on the bipedal All Terrain Defense Pod, and was nicknamed the Duchess. The Duchess generated an energy pulse capable of targeting and superheating a specific material whose nature depended on the settings; initially, it was designed to specifically target the beskar alloy found in Mandalorian armors. At full power and range, it could theoretically annihilate entire armies at a time.
When she created the Duchess, Sabine Wren saw it as a mere challenge to her talent, but did not believe that the Galactic Empire would actually use it, let alone against her own people. However, tests were undertaken, prompting a regretful Wren to sabotage the prototype and destroy the plans, before running away from the Academy.
Years later, the Imperial governor of Mandalore, Tiber Saxon, managed to resurrect the project and used the reconstructed Duchess against Clan Wren when Sabine and her new allies, the Rebellion against the Empire, came to Mandalore to free her father, Alrich Wren. After the Mandalorian warriors were reduced to dust, the rebels and their Mandalorian allies, including Lady Bo-Katan Kryze, decided to infiltrate Tiber Saxon's Star Destroyer in order to destroy the prototype and the plans once and for all. Wren and Kryze, however, had fallen into a trap. Upon reaching the seemingly unsupervised arc generator, they were hit by a non-lethal energy impulse. Saxon then appeared, revealing that he would let both intruders live if Wren agreed to upgrade the weapon so it would operate at full capacity.
Pretending to yield, the former Imperial cadet modified the generator's setting so it would target plastoid alloy rather than beskar. Because all of the Imperial stormtroopers and Governor Saxon wore plastoid-based armor, they were hit by the energy pulse and pinned to the ground. For a moment, Wren watched her enemies wriggle in pain, and briefly toyed with the idea of keeping the Duchess to use in the Alliance's fight against the Empire. But Kryze brought her back to her senses, and Wren destroyed the device for good by slashing it with the Darksaber, breaching its power core. Elsewhere aboard the Star Destroyer, her Jedi friends Kanan Jarrus and Ezra Bridger, and the astromech droid Chopper, managed to wipe all data pertaining to the machine before the overloading Duchess exploded, destroying the AT-DP Arc Cannon Prototype, Governor Saxon, and the entire ship, preventing the Empire from recreating the weapon.
- Star Wars Rebels – "Trials of the Darksaber" (First mentioned) (Indirect mention only)
- Star Wars Rebels: Heroes of Mandalore (First appearance)
- (Indirect mention only)
- (First identified as AT-DP Arc Cannon Prototype)