The main antagonist in JFO is the Inquisitor, Second Sister. She is part of the Inquisitorious; a group of force users turned to the dark side and working for the empire to hunt down Jedis and force users following the purge of Order 66. The Inquisitorious were originally established by Dave Filoni and each inquisitor had a unique weapon, uniform and helmet design.
For JFO, we wanted to create our own Inquisitor and tie her backstory to Cal's. Spoiler alert here!
Trilla was the padawan of Cere Junda who, under torture, gave up her location to the Empire. Her design was inspired by combining some Empire language with a fencer martial arts style. These design cues are found in a full face helmet as well as the shoulder pads, stance, fighting form and of course, the iconic single bladed saber.
We also tried to subtly insinuate her murderous intentions by integrating a red color into her in-stitching, glove palm, jacket lining and cloak lining.