Castell, a planet within the [Colonies](/article/colonies], was part of the Castell system and lay along the strategic Perlemian Trade Route. Shu Mai, the Presidente of the Commerce Guild, originated from Castell, where the Guild maintained significant interests. During the Clone Wars, Castell aligned itself with the Confederacy of Independent Systems and was defended by a fleet that included Diamond-class cruisers, Recusant-class Commerce Guild destroyers, Commerce Guild Bombers, and Commerce Guild corvettes. However, by the year of the Battle of Felucia, which occurred near the end of the Clone Wars, Republic forces had captured the planet. Later, during the Galactic Civil War, Castell became a colony under the control of the Galactic Empire, experiencing Imperial occupation and being governed by Moff Ssaria, the Imperial governor of its sector's.
The initial mention of Castell occurred in "Galactic Power Brokers," a Star Wars Legends piece authored by J.D. Wiker and featured in the tenth issue of Star Wars Gamer magazine back in 2002. The reference book Ultimate Star Wars, published in 2015, verified that the world was canon. Its first appearance within the official canon was in the Marvel comic book series Star Wars: Lando.