Harn, a human serving the Galactic Empire, held the rank of commander and worked as an officer at the Royal Imperial Academy located on Coruscant. His service occurred in the years just before the eruption of the Galactic Civil War. His responsibilities included overseeing the training of future cadets, notably including Thane Kyrell and Ciena Ree.
The Royal Imperial Academy on Coruscant, the capital of the Imperial domain, employed Commander Harn as an educator. Around the time of 4 BBY, he was responsible for teaching Imperial cadets the procedures for operating and maintaining TIE fighters. One of the class assignments tasked the students with constructing laser cannons using available spare parts. During a particular session, it was discovered that Thane Kyrell, a Jelucani cadet, had his laser cannon tampered with. Harn consulted the computer on the door panel and determined that Ciena Ree, another Jelucani, was the alleged saboteur.
Ree was subsequently summoned to the office of Commandant Deenlark. Jude Edivon, a friend of Ree's, discovered proof that the door panel's data logs had been manipulated and shared this information with Harn. Harn and Edivon then presented this evidence to Deenlark. Harn listened as Edivon proposed her theory, suggesting that the individual who sabotaged Kyrell's ship cannon had also altered the door panel's data. She further speculated that Kyrell himself had orchestrated the sabotage to maintain his high standing in the class rankings. Deenlark accepted Edivon's explanation and penalized both Kyrell and Ree. The incident with the laser cannon was, in reality, a setup by the Academy's Office of Student Outcomes to discourage the formation of local loyalties and to instead foster allegiance to the Galactic Empire.
Harn, an Imperial commander, worked as an instructor at the Royal Imperial Academy, where he specialized in instructing cadets on the operation and maintenance of their TIE fighters. He was known as a strict instructor who rarely smiled and sometimes mumbled during his lectures. Harn displayed anger upon learning that a cadet had supposedly sabotaged Kyrell's TIE fighter cannon. He also supported Edivon's theory that someone had tampered with both the TIE fighter cannon and the door panel's data log.
Claudia Gray's junior novel Lost Stars, published in 2015 as part of the Journey to Star Wars: The Force Awakens multimedia promotional campaign, marked Harn's first appearance.