During the first year of the Clone Wars, the CIS developed the C-B3 cortosis battle droids (a B2 Super Battle Droid variant) to give them an edge over the Republic’s elite Jedi and clone troopers.

In that book, the Separatist Alliance finds a mine full of Cortosis and plan to cultivate it in order to make a series of Battle Droids that would be unstoppable to the Jedi and their lightsabers.

Episode 5 featured an epic battle between the Jedi and the newly ... which fans quickly identified to be made of Cortosis — a metal that is not only resistant to lightsabers but also briefly ...