Gundo was a Mirialan male, serving as a lieutenant within the Republic Army's Eighty-sixth Infantry during both the Cold War and the Galactic War against the re-emergent Sith Empire. By the year 3642 BBY, Gundo found himself stationed at a research facility situated on the planet Quesh, working alongside Sajar, a Jedi Padawan who once held a position on the Dark Council. When Imperial forces invaded Quesh and launched an assault on the facility, Gundo took charge of his detachment, leading them in the defense of the installation. He was aided by the Jedi Knight celebrated as the Hero of Tython, working together to prevent the Imperial Military from capturing Sajar.
Gundo, a Mirialan of the male gender, had joined the ranks of the Republic Army and achieved the rank of lieutenant within the Eighty-sixth Infantry by the year 3642 BBY. During the period of the Cold War between the Galactic Republic and the Sith Empire, Gundo was assigned to the planet Quesh, where his unit was tasked with guarding a Republic research facility. This facility focused on studying Quesh's unique environment with the goal of enhancing the planet's adrenal production. Sajar, a Jedi Padawan who had previously been a member of the Sith Empire's governing Dark Council during the prior war, joined Gundo's men. Sajar had been persuaded to renounce the dark side by Jedi Master Tol Braga. Braga dispatched his Padawan to the relatively tranquil Quesh, allowing the Human to meditate on the Force while still serving the Republic. However, in 3642 BBY, Quesh was invaded by the Empire.

While defending the facility, Gundo's troops apprehended several Imperial scouts, and these prisoners were presented to Sajar for interrogation. However, Sajar yielded to his anger and killed the prisoners, subsequently misleading Gundo about his involvement in their deaths when questioned. Nevertheless, some Imperial forces successfully located the research facility and approached the base, prompting Sajar to confront their commander and use telekinesis to hurl the bodies at the enemy. The Imperial officer recognized Sajar, warning the former Sith that the Emperor's Wrath, the personal executioner of the Sith Emperor Lord Scourge, was coming for him. To Gundo's disappointment, Sajar withdrew and refused to engage the enemy, fearing a return to the dark side, leaving the Lieutenant to prepare the base for the impending attack.
Under Gundo's command, the Eighty-sixth's engineers hastily constructed several ray shields capable of sealing the base, but there was insufficient time to fully deploy the devices. As his engineers raced to establish the defenses, Gundo was relieved by the arrival of a second Jedi—the Jedi Knight known as the Hero of Tython, dispatched by Sajar's Master to investigate after Sajar ceased communication with Braga. The Hero and a companion engaged in conversation with the Padawan, uncovering the reasons behind Sajar's reluctance to fight or communicate with Braga. However, Gundo interrupted the Jedi's discussion, bringing news of the base's dire situation. After informing the Hero about the defenses, the Lieutenant requested the assistance of both the Knight and Sajar in defending the main entrance, allowing his engineers to complete the setup of the ray shields.

Choosing not to risk Sajar's potential fall to the dark side, the Hero instructed the former Sith to aid the engineers in setting up the ray shields. The Knight and a companion then hurried to defend the facility. As the pair steadily fought their way back to the main entrance, eliminating the Imperial attackers along the way, Gundo secured the other entrances with his men before rushing to assist the Jedi. Just as the Lieutenant reached the main entrance alongside the Hero, he received notification from his engineers that the ray shields were operational. Gundo promptly activated them from a nearby console. Elated by their success, Gundo assured the Knight that his unit could hold out until reinforcements arrived—but his words were cut short by movement detected outside the shield.
To the surprise of both Gundo and the Knight, a Sith Pureblood—the Emperor's Wrath—approached the shield, exchanging cryptic remarks with the Hero before departing. Relieved that the immediate threat had subsided, Gundo thanked the Knight and reported that Sajar's assistance had enabled the engineers to set up the ray shields in half the expected time. The Lieutenant remained at his post near the entrance while the Knight went to speak with Sajar, and he continued to guard the research facility with the rest of the Eighty-sixth Infantry detachment even after Sajar departed to the Jedi homeworld of Tython to meet with his Master regarding his close encounter with the dark side.

Gundo, a Mirialan male with olive skin, black hair, pink eyes, and distinctive black facial tattoos, was one of many members of his species serving within the Republic Military in the aftermath of the Great Galactic War. Gundo was known as a composed soldier and a capable commander during battle, avoiding unnecessary words during tense situations. Upon the arrival of the Hero of Tython during the fighting, Gundo calmly accepted the Knight's presence and immediately treated the Jedi as a valuable strategic asset, requesting the Hero's assistance in defending the main entrance without questioning the stranger's identity.
As a member of the Eighty-sixth Infantry, Gundo wore white and grey armor adorned with gold markings and a pauldron on his left shoulder. He was also equipped with a standard-issue blaster rifle, but he chose not to wear a helmet during combat.
Gundo made his initial appearance in the Jedi Knight mission titled "The Emperor's Wrath" within Star Wars: The Old Republic, a video game developed by BioWare and published by LucasArts. The mission presents a significant alignment choice: determining Sajar's role during the battle. Forcing Sajar to fight results in the player gaining dark-side points, as his descent into the dark side accelerates during combat. Conversely, instructing him to remain behind or assist the engineers yields light-side points.