G-90, also known as Gee-Ninety, functioned as an assassin droid manufactured by Jayosbrand. During the Imperial Era, it served the Assassin's Guild. This droid was characterized by its large, spherical body, topped with a protruding head.
Gee-Ninety, also known as G-90, was contracted, along with Chilla Zin and Loriach, to assassinate a pontiff who had formed an alliance with the Crimson Dawn criminal organization. This assignment was a test given by the Sith Lord Darth Vader as part of his mission to dismantle the syndicate. Vader subsequently terminated Gee-Ninety when the droid made an attempt to release prisoners from torture.
Following his destruction by Vader, Gee-Ninety was rebuilt by Jul Tambor, as were many other droids. He then joined Tambor's anti-Imperial organization. During the outreach mission to the planet Brentaal IV, Gee-Ninety aided Tambor but alerted him to the fact that Sabé was an agent of Vader. Tambor acknowledged this, stating he hoped to persuade her to join their cause. After a bombing of Kantiema discredited Tambor, his efforts to liberate Skako Minor failed. Gee-Ninety journeyed to Skako Minor, where Sabé destroyed him after she returned twelve Skakoan refugees to the world.