A terrestrial world located along the Perlemian Trade Route, the Gossam homeworld was reached by other sentient species during the blazing of that route between 30,000 BBY and 25,000 BBY. Having begun experimentation with the tumble hyperdrive during the Infinite Empire's reign over parts of the galaxy, the Gossam Courivers were able to leave Castell and colonize planets such as Felucia circa 27,000 BBY. When the Galactic Republic was born out of the Core Worlds, Castell joined the rapidly expanding government sometime before 22,000 BBY.
Involvement in galactic history was rare for Castell, remaining within Republic space even during times of conflict. During the Great Sith War, the Krath waged a Holy Crusade along the worlds of the Perlemian in their attempt to conquer Coruscant. Recovering from the war, the Republic would race along the Perlemian and its worlds during the Jedi Civil War to engage the armies of Revan's Sith Empire.
In 19 BBY, following Presidente Mai's execution along with the rest of the Separatist Council on Mustafar by Darth Vader, the war ended and the Galactic Empire arose from the ashes of the Republic. Because of their former allegiances, the Gossams of Castell were targeted by the Empire for enslavement, and the factories of the world were repurposed to manufacture military goods for the Imperial Navy. Undoing any of the meager good that Shu Mai and the Commerce Guild had managed to achieve, Castell spiraled back into economic turmoil under the Empire and was unable to supply many soldiers to the fledgling Rebel Alliance, though many expressed support for the group. When the Rebel Alliance eventually emerged victorious over the Empire, it took a year for the New Republic to move down the Perlemian, liberating Castell in 5 ABY. Struggling to recover despite their newfound independence, the world suffered greater setbacks during the Yuuzhan Vong invasion of the galaxy. Conquering Castell, the world was ravaged by the invaders until the New Republic forced itself down the Perlemian once again, from Dac to Coruscant. With the rise of the Galactic Alliance, Castell once more began the recovery process. As of 127 ABY, Castell fell within the area controlled by the Empire of Darth Krayt.