The Galactic Empire maintained a detention center known as Kalist Base. It was situated on Kalist VI, a planet located within the remote Deep Core region. This prison was composed of a large dome crafted from transparisteel, and the perimeter was secured by a landing platform and a series of electrified barriers.
From the early years of the New Order, the Kalist VI penal colony served as a holding area for various individuals, including political objectors and captured soldiers. Among these political prisoners were the parents of Dak Ralter, who were descendants of the Old Republic. Ralter himself was born while his parents were incarcerated within the facility.
Having been born inside the prison's walls, Ralter's perception of the galaxy was one of dread, oppression, and Imperial rule. His limited understanding of the outside world was derived from the stories shared by his parents and the fragmented information he gleaned from newly arrived inmates. He yearned for freedom. His chance at liberation materialized when he encountered Breg, a new prisoner who revealed himself to be a starfighter pilot from the Alliance to Restore the Republic, shot down during a reconnaissance mission. The pair orchestrated an escape by scaling the inner and outer electrified fences and appropriating two guard uniforms. They then initiated a fabricated reactor alert, engineered a planned power failure, and commandeered an Imperial prison barge, using it to flee the planet. During their flight, Breg sustained a fatal wound inflicted by an Imperial stormtrooper, but Ralter survived and embarked on a new life with the Rebellion.
Around eight months following the Battle of Yavin, the Empire transported Jabiimi prisoners, along with Jorin Sol, to this installation. The Jabiimi were forced into slave labor, while Sol was subjected to torture in an attempt to extract information about the location of the Alliance Fleet. A Rebel team, including Luke Skywalker, successfully infiltrated the base by disguising themselves as the crew of the Imperial tanker Nuna's Twins, with the objective of rescuing Sol. By drawing the majority of the base's personnel away from the planet and into a trap, the Rebels were able to liberate Sol and the other prisoners, inflicting significant damage on the facility. Following this assault, the base underwent rapid repairs and reinforcements.