Kalast was a Moff who committed treason against the Galactic Empire during the era of the Galactic Civil War.
He utilized the Bothan Spynet to procure highly classified, top-priority Galactic Empire codes pertaining to the Death Star, subsequently delivering this vital information to the Rebel Alliance. Later, he rendezvoused with the Alliance at a clandestine facility situated on Thyferra. Determined to unmask the traitor, Darth Vader located him on Thyferra and spearheaded an assault force on the planet. Kalast managed to evade capture due to the early detection of the approaching Imperial fleet by a sensor system.
He then took refuge above Atzerri aboard a prototype Imperial II-class Star Destroyer called the Avenger. His Star Destroyer was conspicuously adorned with red markings, signifying his allegiance to the Rebellion. The Empire tracked him down to this location, prompting the Imperial Navy to converge upon the system. Kalast initiated a jump to hyperspace and successfully escaped. Following the siege of his Atzerri hideout, he fled to various planets, until his escape was cut short by an Immobilizer 418 cruiser. His flagship sustained significant damage, leading to his surrender.
He was personally interrogated by Emperor Palpatine and, subjected to torture, confessed to providing the top-secret plans to the Bothans. Once his usefulness had expired, Kalast was executed for his act of treason.