The octuptarra tri-droid, also known simply as the octuptarra droid or tri-droid and nicknamed the "virus droid" due to the biological plagues it sometimes carried, was a model of three-legged droid walker manufactured by the Techno Union. Produced in a number of different sizes, including agile octuptarra combat tri-droids and gigantic octuptarra magna tri-droids, they were used by the Confederacy of Independent Systems during the Clone Wars.
The larger and more dangerous counterpart of the DSD1 dwarf spider droid, the octuptarra tri-droid, also known simply as the octuptarra droid or tri-droid, was a model of fourth class battle droid walker. Their large heads contained their cognitive modules and sensor suite. Three red photoreceptors allowed them to look in every direction at once, leaving them with virtually no blind spots and making them almost impossible for enemy troopers to attack by surprise from behind. Fully shieled from such offensives, the octuptarra's body was protected from electric-based attacks. The powerful hull was even resistant to the Zaly Shield's blasts.
They had an omnidirectional field of fire, with typical octuptarra tri-droids being armed with three rotating laser cannons placed equidistant below its photoreceptors and around its central stalk, which could spin around and lock onto targets from any side in an instant. They had three triple-jointed, hydraulic limbs that allowed them to scale steep surfaces. However, its three-legged design was its primary weakness, as if one was damaged, the entire droid would topple over. In addition, they were also slow-moving and vulnerable to tripping.
An octuptarra combat tri-droid on Utapau.
Octuptarra tri-droids were produced in a number of different sizes during the Clone Wars. Agile, battle droid-sized versions, known as octuptarra combat tri-droids, stood 3.6 meters in height and featured a highly-mobile chassis. Primarily used as anti-personnel platforms, certain variants stored airborne biological plagues in their bulbous heads, allowing them to wreak havoc on the enemy long after the unit is destroyed, causing them to be nicknamed "virus droids." The largest models, known as octuptarra magna tri-droids, stood at 14.59 meters in height and were used as combat artillery. Large enough to take on heavily armored All Terrain Tactical Enforcers, their laser cannons could be replaced with chain-fed missile launchers.
The octuptarra tri-droid was named for the octuptarra, an eight-eyed, gasbag-headed vine walker found on Skako. At least when corrupted by the Scourge, an octuptarra was able to speak Galactic Basic Standard. A variant of the octuptarra magna tri-droid used on the planet Skako Minor was equipped with an engine at its waist, creating enough thrust to allow it to hover many meters above the ground.
Tri-droids were used by the Separatists during the Clone Wars.
The octuptarra tri-droid was primarily manufactured by the Techno Union division of the Separatist Droid Army, who often fielded them in battle during the Clone Wars. In the year 22 BBY, octuptarra magna tri-droids were deployed during the Battle of Christophsis, with several being destroyed due to the intervention of Jedi General Anakin Skywalker and Torrent Company clone troopers with him. Later in the battle, several were stationed outside of the Separatist deflector shield. In 19 BBY, octuptarra magna tri-droids were used to guard the city of Purkoll, headquarters of the Techno Union, on Skako Minor. Towards the end of the Clone Wars, octuptarra combat tri-droids were used to protect General Grievous' Pau City headquarters during the Battle of Utapau. Concurrently, both variants were used by the Separatist in a battle on Mygeeto.
The Scourge finds and corrupts an octuptarra tri-droid in the abandoned Techno Union factory.
After the Galactic Republic was replaced by the Galactic Empire, most octuptarra tri-droids were deactivated. One octuptarra was left abandoned in the secret Techno Union droid factory of Mustafar, where it remained all the way until the scourge of the droids. The Scourge, having corrupted ZED-6-7 with a spider-droid and entering the factory as both, found and corrupted the octuptarra, which the Scourge used to erupt from the ground to attack the Sith Lord Darth Vader and the droid uprising. The powerful octuptarra body protected the Scourge from Vader's electrostaff and Zaly Shield, which Vader was forced to rely on instead of his Force powers during the Force Wave. Through his battle with the octuptarra, however, Vader regained his control over his Force powers. As such, Vader was able to destroy the corrupted octuptarra.
Early concept art of what became the octuptarra tri-droid, by Ryan Church.
The octuptarra tri-droid was originally created for the 2005 film Star Wars: Episode III Revenge of the Sith. It was first identified in Star Wars: Absolutely Everything You Need to Know, a reference book written by Adam Bray, Kerrie Dougherty, Cole Horton, and Michael Kogge and released on September 4, 2015. Several variants of the octuptarra tri-droid were visible in Revenge of the Sith; The octuptarra combat tri-droid found on Utapau had its digital model scaled up and modified to become the octuptarra magna tri-droid seen on Mygeeto, with slight cosmetic alterations between the two such as the former's laser cannons being replaced with chain-fed guns on the latter. The octuptarra tri-droid could be found in early sketches of Utapau by Ryan Church.
According to Pablo Hidalgo of the Lucasfilm Story Group, small and large octuptarra droids found their names combined by the time of the Star Wars: The Clone Wars series. In Legends, small units were originally called octuptarras, whereas the larger units were known as tri-droids at that time. The large variant was given the name octuptarra magna tri-droid in Star Wars: The Clone Wars: Incredible Vehicles.