Gadon Thek served as the chieftain of the Hidden Beks, a swoop gang that made their base of operations in the Lower City on Taris. He frequently clashed with Marn Hierogryph, whom he disparagingly called a "rodent."
Despite his deep connections to the criminal elements of Taris, Gadon was generally viewed favorably by the inhabitants of the lower city, offering protection to his loyal followers and providing assistance to the impoverished. However, he harbored resentment towards the Sith presence and was deemed a threat by them.
During the Mandalorian occupation of Taris, Gadon spearheaded the Hidden Beks' resistance against the occupying forces. Acknowledging the limitations of leading a mere gang rather than a formal army, he sought an alliance with the Taris Resistance. However, the Resistance hesitated to collaborate with a group they considered beneath them, a sentiment reinforced by the presence of Taris' constable, Sowrs. Blaming the Beks for the abduction of her children, she adamantly refused to negotiate with Gadon.
The arrival of Zayne Carrick presented Gadon with an opportunity to engage with the constable, using the wanted "Jedi killer" as a bargaining chip. This proved unnecessary when Zayne, Gryph, and Mission Vao uncovered that Brejik, a member of Gadon's gang, had captured the constable's children and that Griff Vao was caring for them. Although angered by the actions of Brejik and Griff Vao, Gadon saw an even better opportunity to gain favor with the Resistance. He led the Beks to the Resistance headquarters to negotiate a temporary alliance.
Falsely claiming that Zayne was responsible for finding the constable's children, Gadon successfully persuaded the Resistance's leader, Taris Senator Haydel Goravvus, to cooperate with them. Furthermore, he shielded the fugitive Raana Tey from capture, asserting that Carrick was one of the Beks.
Subsequently, Gadon assisted in planning the bombing of the Jedi Tower with the intention of eliminating the Mandalorian leader Cassus Fett. Gadon guided the group to the Tower's foundation, utilizing the underground tunnels to gain access, and aided in setting up the explosives. However, the mission quickly deteriorated when it was discovered that Fett had already left the building and that the Mandalorians had launched an assault on the Resistance headquarters. While the rest of the Beks retreated to the Pit, Gadon and Gryph remained behind, hoping to rescue Zayne and Shel Jelavan, who were still trapped inside the Tower. After dropping a line to Zayne and Shel, Gadon managed to narrowly escape the pursuing Mandalorians.
Thek would later be involved in a swoop bike accident where he lost his sight. However, this was partially recovered with ocular implants.
Following the accident, it was widely believed that Brejik, Gadon's most capable follower and adopted son, would assume leadership of the gang due to Gadon's injuries. However, Gadon felt that Brejik was not yet ready to take over and that he was still capable of leading the gang. This public rebuke angered Brejik, and in a fit of rage, he and younger members of the Hidden Bek gang defected and joined their rivals, the Black Vulkars. Soon after, Brejik and his followers seized control of the Black Vulkar gang and initiated a gang war to eliminate the Beks and dominate the Lower City. Unlike the Beks, the Vulkars openly and shamelessly engaged in illicit drugs and slavery. The resulting gang war caused significant hardship for the citizens of the Lower City, as the Vulkars indiscriminately targeted not only Hidden Beks but also any other individuals they encountered.
When Revan crash-landed on Taris, he sought Gadon's assistance and recovered a prototype accelerator that had been stolen by the Vulkars. Gadon informed Revan that the accelerator was located in their base. After traveling through the Undercity, Revan reached the base and retrieved the accelerator. Using the accelerator, Revan secured the freedom of Bastila Shan, who had been captured and held captive by the Vulkars. Taris was subsequently destroyed by Darth Malak through orbital bombardment.
During the mission to retrieve the accelerator, Kandon Ark, a member of the Vulkars, extends an offer to the player character, Revan. If Revan assassinates Gadon, the player will be allowed to race for the Vulkars and earn 500 credits. Revan would gain a dark side point as a consequence, but the subsequent events would remain unchanged.