Hacklin was a male admiral within the Imperial Navy. He was a staunch supporter of Darth Angral, a Sith Lord belonging to the re-emergent Sith Empire during their Cold War conflict with the Galactic Republic. After the Admiral's path crossed with the Jedi Padawan Kira Carsen following her capture by Angral's forces, the Child of the Emperor known as Valis assumed Hacklin's identity. This deception was part of a scheme to ensnare Carsen and her Master in a trap located on a derelict mining facility.
During the Cold War against the Galactic Republic, Hacklin served as a male admiral in the Navy of the Sith Empire. Furthermore, he acted as both an adviser and an ally to the Sith Lord named Darth Angral. In the year 3643 BBY, Hacklin went with the Sith to the Ord Mantell Orbital Station following Angral's spies detecting the presence of the Jedi Padawan Kira Carsen on that space station. Angral, motivated by a desire to avenge the death of his son, Tarnis, and thus searching for Carsen's Master, interrogated Carsen alongside Hacklin and the Inquisitor Ferav. However, Carsen successfully misled the three, convincing them that the Jedi Knight was located on Corellia. Hacklin and Angral then left the station to supervise the installation of the Desolator superweapon onto Angral's flagship, the Oppressor.
Shortly after these events, Valis, a Child of the Emperor, adopted Hacklin's persona in order to lure Carsen—herself a former Child—and her Master, hoping to capture her in an attempt. Valis, posing as Hacklin, made contact with Republic General Var Suthra, asserting a desire to defect and requesting a meeting with the Knight and Carsen. To bolster the ruse, Valis also spread rumors that the Admiral had been issued a death mark. When the Knight and Carsen arrived at the abandoned mining facility in the Unknown Regions chosen by Suthra, Valis revealed to the pair that Hacklin remained utterly loyal to the Empire and Angral, before apologizing for the trickery.
Hacklin's character was developed for Star Wars: The Old Republic, a video game that BioWare launched on December 20, 2011. The character is initially mentioned in the Jedi Knight class mission titled "New Intelligence," but his name is not revealed until "The Defector," where Valis, a Child of the Emperor, uses Hacklin's identity to bait Kira Carsen and the player.