Cortosis droids were a line of Droids that where built using the same design of the B-1 Battle Droids, with the major improvement in design, that being the improved building material, Cortosis, hence the name. It was designed after the Trade Federation' Magna Guards. The Cortosis Droids were designed by the Trade Federation early in the Clone Wars, but were destroyed when Palpatine revealed its' factories location to the Jedi Knights. But somehow the plans for this droid escaped the factories on Cato Nemoidia, and were taken to Viceroy Nute Gunray, he in turn gave them to Gizor Dellso which took them to Macnemere where he would later build them.