Jak, a Nautolan of the male gender, was raised in the Coruscant underworld, developing a friendship with Cade Skywalker, a Jedi Padawan who frequented the planet's lower levels. By the year 137 ABY, Jak's occupation was the personal bodyguard for the Hutt Queen known as Jool, and he also worked as an enforcer at Rik's Cantina, an establishment owned by her. His dedication to Jool was absolute; he would remove anyone causing problems for her at her request. In 137 ABY, Skywalker made a visit to the cantina, but he was soon captured by the Sith ruling Coruscant; Jak later observed a hologram that Skywalker had embedded within his astromech droid, identified as R2-D2. Following the hologram's conclusion, a group of Skywalker's comrades initiated planning for a rescue mission to free him from the Sith's grasp, but Jak opted out of the mission and departed the cantina.
During the Sith–Imperial War spanning from 127 to 130 ABY, Jak, a male Nautolan, resided in the underworld of Coruscant, the galactic capital. In his younger years, Jak frequently encountered and eventually formed a bond with Cade Skywalker, a Jedi Padawan, who visited the planet's underlevels to escape the demands of his rigorous Jedi training. By the time 137 ABY arrived, Jak held the position of personal bodyguard to Queen Jool, the Hutt proprietor of Rik's Cantina, a prominent bar and gathering place in the Coruscant underworld. Furthermore, Jak acted as the cantina's enforcer, becoming such a common sight that his presence often went unnoticed by the establishment's patrons.
In the year 137 ABY, Skywalker made his way back to the cantina. Jak was taken by surprise at the sight of his old friend, considering the Jedi Order had been decimated by Darth Krayt's Sith Order seven years previously, and Krayt had usurped the galactic throne located on Coruscant. Regardless, the two exchanged a casual greeting at the entrance. Skywalker, who was on his way to the Temple of the Sith with the intention of rescuing the captive Jedi Hosk Trey'lis, entrusted Jool with the access codes to his starship, the Mynock, in case he did not return. Shortly after, his co-pilot Jariah Syn and mechanic Deliah Blue arrived and collected the codes. Jak and Jool joined them within the cantina, witnessing a hologram that Skywalker had stored within his astromech droid R2-D2, instructing them not to attempt a rescue. Shortly thereafter, the bounty hunters Chak and Kee arrived, harboring their own reasons for wanting Skywalker rescued, along with Morrigan Corde, Skywalker's mother. Upon Jool's command, Jak escorted her back to her residence while the diverse group remained in the bar, strategizing the best approach to retrieve Skywalker from the temple.
Jak possessed black eyes and skin of a green hue. Serving as Jool's bodyguard, Jak demonstrated unwavering loyalty to the Hutt. His primary concern was her protection, and he addressed troublemakers within Rik's Cantina at her direction by forcibly removing them from the premises. Characterized by a strong and silent demeanor, Jak's presence often faded into the background for the bar's patrons as he maintained watch over the entire room, particularly vigilant when unfamiliar individuals entered. Despite his surprise at seeing Cade Skywalker in 137 ABY, Jak greeted his old friend with only a single word upon Skywalker's arrival at the cantina. He was content in his role as hired muscle, free from the burden of excessive thought, and had no objections to abstaining from the rescue operation aimed at freeing Skywalker from the Temple of the Sith.
While stationed on Coruscant, Jak typically wore brown clothing.
Jak made his debut appearance in the fourteenth issue of the Star Wars: Legacy comic series. This issue was authored by John Ostrander and Jan Duursema, with illustrations by Duursema, and was published by Dark Horse Comics on July 11, 2007.