Firmus Piett was the final admiral of the Imperial Navy's Death Squadron, Darth Vader's personal fleet of Star Destroyers. Coming from humble beginnings on the backwater Outer Rim world of Axxila, Piett began his naval career with the Axxila antipirate fleet. Though his posting was not notable, Piett's creativity and dedication made his home sector the safest in the Outer Rim. His ascension through the ranks, however, was not so much a tribute to his dedication, but his ability to shift blame onto others when mistakes were made. With an extraordinary number of arrests and suppressions to his name, as well as what appeared to be a perfectly clean record, Piett earned the attention of high-ranking officers on Imperial Center.

Transferred to the Imperial Navy, Piett was picked out to serve in Vader's Death Squadron, which prowled the galaxy searching for Rebel Alliance headquarters. Given the captaincy of the Imperial II-class Star Destroyer Accuser, Piett served diligently until the command of the fleet's flagship, the Star Dreadnought Executor, was vacant. As captain of the Executor, Piett relentlessly searched for the hidden Alliance base while secretly undermining his superior, Admiral Kendal Ozzel. At the Battle of Hoth, Ozzel was summarily executed by Vader for incompetence, allowing Piett to swiftly step into the admiral's role.

Though he was criticized for his swift ascent to the top of the command chain, Piett set himself about his task with enthusiasm, though he feared that he would meet the same fate as Ozzel. He made several potentially fatal blunders soon after his promotion but was able to shift blame as he had done in the past. Following the failed capture of Luke Skywalker at Bespin, the Executor was taken back to Imperial Center, leaving Piett to command the Accuser once more. In 4 ABY, though, Piett was once again on the bridge of the Star Dreadnought, commanding the Imperial fleet in the Battle of Endor. Piett perished in the battle when an RZ-1 A-wing interceptor piloted by Arvel Crynyd rammed into the Executor's bridge.