The C-B3 cortosis battle droid represented a battle droid design that bore similarities to the B2 super battle droid. The Techno Union engineered the C-B3 with the specific intent of engaging Jedi forces during the Clone Wars.
Their external armor was constructed from cortosis, a material capable of deflecting lightsaber strikes. The black exterior plating was tightly fitted to the droids' frame. These droids also possessed an intelligence matrix identical to that of the B2 super battle droid. However, unlike the B2, they lacked hands with gripping capabilities, as their arms terminated in dual high-intensity laser cannons. The wrist's ball joint enabled the cannons to rotate nearly 360 degrees. The droids could also employ their arms as shields against lightsaber blades.
Anakin Skywalker discovered a vulnerability in the droids' armor regarding lightsabers. A precisely aimed, descending lightsaber strike targeting the narrow space between the two breastplates could bisect a cortosis droid's torso.
Manufacturing commenced when Wat Tambor pitted two internal teams against each other in a competition to design the Separatist B3 unit. The Avatar-7 was chosen over the cortosis battle droids, leading to the cortosis droids being produced as the C-B3.
The C-B3 droids saw their initial, limited deployment on Tatooine, but were utilized more extensively during the attack on Coruscant and in the defense of the Techno Union foundries located on Metalorn. Their performance proved to be highly effective—perhaps too effective, from the perspective of Darth Sidious. Concerned that they could shift the war's outcome, Darth Sidious, secretly Supreme Chancellor Palpatine, leaked information regarding the droids' location on Metalorn to the Jedi Order.
The production of C-B3 battle droids ceased when Anakin Skywalker destroyed the Metalorn factory ten months following the First Battle of Geonosis.