Tantor served as a general within the armed forces of the Alliance to Restore the Republic. This individual, General Tantor, was present at a top-secret meeting of Alliance High Command which took place on Zastiga. During this meeting, they were informed about the DS-2 Death Star II Mobile Battle Station's existence. Tantor, along with Rebel Alliance Special Forces commander General Crix Madine, were required to develop a strategy for infiltrating Endor, the location of the Death Star II's deflector shield generator.
Following Han Solo's rescue, the Alliance's leadership held a briefing aboard Home One to outline the strategy for the impending Battle of Endor. General Tantor, along with numerous other high-ranking Alliance figures, was in attendance.
During the Galactic Civil War against the Galactic Empire, Tantor held a distinguished position as one of the leading generals within the Alliance to Restore the Republic. Not long after the Battle of Hoth, Tantor participated in a highly confidential assembly of the Alliance leadership situated in a Rebel safe house on the planet of Zastiga. During this assembly, Chancellor Mon Mothma revealed that the Alliance had become aware of the Empire's construction of a second Death Star above the moon of Endor. On the meeting's second day, Princess Leia Organa suggested leading a small team on a mission to the Corva sector as a diversion for the Empire while the Alliance Fleet prepared for the upcoming Battle of Endor.
General Crix Madine offered to safeguard Organa during the mission, but Admiral Gial Ackbar argued that both Madine and Tantor were essential for planning the infiltration of Endor by a team of Rebel commandos. Consequently, Madine dispatched the commando Lokmarcha with Organa, whose mission was successful, enabling the fleet to assemble in the Sullust system. General Tantor was present alongside Madine and other high-ranking Alliance officials. Ultimately, the Alliance succeeded in destroying the second Death Star and achieving victory in the Battle of Endor.
Tantor's debut in Star Wars canon occurred in 2015 with their appearance in Moving Target: A Princess Leia Adventure and its associated audiobook, penned by Jason Fry and Cecil Castellucci. Brenn Tantor was initially conceived for the Star Wars Legends video game Star Wars: Force Commander, which saw its release in 2000.