Gap Nox functioned as a Neimoidian captain within the ranks of the Neimoidian Gunnery Battalion. During the Clone Wars, this battalion served the Confederacy of Independent Systems in their conflict against the Galactic Republic. Following the Battle of Moorja, Nox transitioned into the role of a bodyguard for Nute Gunray, the Trade Federation Viceroy. In 19 BBY, Nox accompanied Gunray to the planet Mustafar, which housed the stronghold of the Separatist Council.
Alongside Lieutenant Fame Drimal, Nox was positioned near the entrance of the war room, on opposite sides. The CIS leadership awaited the arrival of Darth Vader, the newly designated pupil of Darth Sidious, a Sith Lord. Despite being a secret ally, Sidious betrayed the Separatists, leading Vader to slaughter everyone present, including both Nox and Gunray. Nox possessed orange eyes and green-toned skin. The individual wore standard Neimoidian guard armor and carried a Neimoidian ceremonial blaster rifle as their weapon.
The initial appearance of Gap Nox occurred as an extra, without a specific name, in the 2005 motion picture Star Wars: Episode III Revenge of the Sith. Originally, the plan involved depicting their on-screen demise at the hands of Anakin Skywalker, along with Drimal, but this particular scene was ultimately removed. Nine years later, in the "The Devious Neimoidians Revealed" article featured in Star Wars Insider 147, Nox received identification thanks to Tim Veekhoven, Kevin Beentjes, Sander de Lange, and Leland Chee. Further details about the character were provided in the endnotes of the article, which were shared on the Facebook page titled Star Wars Sourcebooks, managed by the first three authors mentioned.