Quell was a largely unremarkable terrestrial planet located in the far reaches of the Quell system and the distant reaches of the galaxy, in the regions known as the Outer Rim Territories and New Territories. Situated in grid square Q-6 of the Standard Galactic Grid, Quell was located along the Salin Corridor hyperspace route, which connected it to the astronomical object Yalbec Prime and the planet Lola Sayu. Viewed from space, the planet's surface was cerulean in color and its atmosphere featured white clouds. Quell had a brown terrain with large spherical formations sprouting out of the ground.
Aayla Secura's forces engaged a Separatist squadron in Quell's atmosphere.
In 21 BBY, during the Clone Wars fought between the Galactic Republic and the Confederacy of Independent Systems, the Republic task force of three Venator-class Star Destroyers, including the Liberty, commanded by Twi'lek Jedi General Aayla Secura came under attack by a Confederacy naval squadron of five Munificent-class star frigates led by the T-series military strategic analysis and tactics droid TF-1726. As the battle raged, Secura's 327th Star Corps clone troopers experienced heavy casualties, while the Republic vessels descended from orbit into the planet's upper atmosphere, where the attacks further intensified. Informed of Secura's situation over Quell, fellow Jedi General Anakin Skywalker and his Padawan, Ahsoka Tano, reached the planet's orbit aboard the Venator-class Star Destroyer Resolute.
Arriving over Quell, as the Twi'lek Jedi lost her accompanying pair of Star Destroyers, Skywalker launched several Low Altitude Assault Transport/infantry gunships from his flagship in order to board the Liberty and rescue Secura. A Republic Consular-class cruiser proceeded to dock with the Libertys lower hangar as per Skywalker's orders in an effort to extract the Jedi and return to the Resolute. However, as the Jedi and several clone troopers boarded the frigate, Skywalker was injured while attempting to hold back an explosion using the Force in order to allow his compatriots to enter the ship. While fleeing from the Liberty—which plummeted to Quell's surface—and returning to the Resolute, the frigate suffered damage from crossfire and was forced to activate its hyperdrive. The vessel thus entered hyperspace, departing to the planet Maridun, while the Republic's remaining forces continued to engage the Confederacy in Quell's atmosphere.
Aayla Secura and the 327th returned to Quell later in the Clone Wars.
After the battle had ended at Quell, the Confederacy had secured an unqualified victory over the Republic, which revealed the latter's struggles in maintaining control throughout the Outer Rim Territories, where acts of separatism had begun to flourish. In addition, the Battle of Quell also underscored how ultimate Republic victory in the war over the Confederacy was not truly certain. Later in the war, between 20 BBY and 19 BBY, Secura and her troops returned to Quell and engaged in a battle on its surface.
Quell first appeared in "Jedi Crash," the thirteenth episode of the animated series Star Wars: The Clone Wars' first season, which originally aired on January 16, 2009. The episode's script described the Battle of Quell as being fought in space, but it was moved to the planet's upper atmosphere for dramatic effect as the show entered pre-production. The planet was first identified in the Episode Guide for "Jedi Crash" on StarWars.com. The surface of Quell was pictured by the "Quell" card included in the Way of the Force wave of the Star Wars: Destiny card game by Fantasy Flight Games. The art used was illustrated by artist Chris Scalf and previously used in the Star Wars Legends continuity to depict the planet Saleucami in the 2012 reference book The Essential Guide to Warfare.