A BX-series commando droid is shown amidst a dioxis cloud.
Dioxis was a poisonous gas utilized by organizations such as the Trade Federation and the Confederacy of Independent Systems. During the Galactic Civil War, dioxis grenades, which released this deadly gas, were deployed.
During the Trade Federation's invasion of the planet Naboo, the Neimoidians made an attempt to kill Qui-Gon Jinn along with Obi-Wan Kenobi. They tried achieving this by releasing the poisonous gas into a conference room aboard their Lucrehulk-class Battleship. However, both Jinn and Kenobi managed to escape the room and fled to Naboo.
During the Clone Wars, Count Dooku incorporated dioxis into a contest that was held on Serenno. In an area called the Box, eleven bounty hunters participated in a series of challenges. The purpose of these challenges was to determine which individuals would be selected for a team tasked with kidnapping Supreme Chancellor Sheev Palpatine. The initial challenge required the competitors, including Kenobi who was in disguise, to escape a room that was being filled with the gas.
Dioxis made its initial appearance in the 1999 movie Star Wars: Episode I The Phantom Menace, which was the first film in the Star Wars prequel trilogy.
For "The Box," an episode of Star Wars: The Clone Wars, the original plan was to have water, instead of dioxis, fill the chamber for the Box's first challenge. Dave Filoni, the supervising director, mentioned that the water effect had not been solved when the story was being written. This led the production team to opt for dioxis. While the water effect was eventually solved, the limited FX budget for the episode meant that they had to stick with dioxis.