Mar Barezz, a male Human officer within the Imperial Security Bureau's Investigations division, was a dedicated follower of Emperor Palpatine and the New Order. His duty involved hunting down spies and traitors throughout the Galactic Empire, regardless of whether they were Rebel escapees or members of the Empire's own military forces. During the Galactic Civil War, Barezz acted as an Imperial Security Bureau advisor during the Raid on Picutorion during the Kwymar Suppressions, and later became rivals with Alliance Intelligence agent Tay Vanis, famously known as "Tiree." Their ongoing conflicts became legendary in intelligence circles. Barezz tried to prevent the agent from enlisting new recruits for the Rebellion, and cornered Vanis when his adversary enlisted four individuals—Raleigh Dawn, Sammie Staable, Raal Yorta, and Smileredon-Verdont—on the planet of Ord Mantell. Pursuing them to the derelict lidium mine Mesa 291 on Bothawui, Barezz led a squad of stormtroopers and attempted to capture the fledgling Rebels to interrogate them and force them to expose the location of the clandestine Rebel base where they were to be taken. During this operation, Raal Yorta hurled a thermal detonator at Barezz and three stormtroopers. The subsequent explosion enabled the Rebels to flee.
As an officer within the Investigations branch of the Imperial Security Bureau, Mar Barezz, a male Human, served the Galactic Empire in the course of the Galactic Civil War. He was present aboard Commodore Bevven's ship during the Raid on Picutorion, which was part of the military campaign known as the Kwymar Suppressions. High Colonel Theol Drost and Bevven, who were in charge of the army and navy detachments, respectively, observed the battle as it unfolded. They discussed whether to deploy TIE/LN starfighter reinforcements to counter the Alliance to Restore the Republic BTL Y-wing starfighters that were attacking Tensiger's 6th regiment. The regiment's armor battalion had broken through the outer defenses of an Alliance tracking station on the surface. As the commodore decided to deploy the starfighters, Barezz politely interrupted and informed Drost and Bevven that the Imperial Security Bureau had flagged Captain Ganig and Sergeant Stecker, two soldiers involved in the assault, as "sensitive." Despite being celebrated heroes for their actions at the Battle of Sagma, the Imperial Security Bureau had noticed their lax attitude toward discipline. Barezz was also certain that Linds, a trooper suspected of sympathizing with the Rebels, had been in contact with both of them. He was concerned about the possibility of two Imperial war heroes defecting to the Alliance. Barezz was certain that the Commission for the Preservation of the New Order would honor the two soldiers again if they survived Picutorion. He believed the risk was too great, despite the absence of evidence suggesting either man intended to defect. He advised Bevven and Drost to delay the reinforcements until Ganig and Stecker were dead, as deceased heroes were just as valuable as living ones for Imperial propaganda purposes. Both officers concurred, and Bevven postponed the TIE reinforcement by ten minutes.

Lord Darth Vader personally tasked Barezz with eliminating Rebel spies and traitors, leading him to become obsessed with stopping Tay Vanis, the Alliance Intelligence agent known as "Tiree." The pair's ongoing struggles became legendary within the Investigation branch. Vanis's responsibilities included recruiting new operatives for the Rebellion. Barezz discovered that Vanis intended to escort a group of six new Rebels to a secret rendezvous aboard a shuttle. With the complete backing of the Imperial-class Star Destroyer Aggressor, Barezz arrived at the rendezvous first, destroying the shuttle and killing all six individuals on board. However, despite Barezz's efforts to encourage the crew of the Aggressor, the Star Destroyer was unable to capture Vanis when he arrived in his T-65 X-wing starfighter. This annoyed the Aggressor's captain, as the Imperial Security Bureau lacked military oversight and it was a courtesy to allow their officers on the bridge of a starship. While the Aggressor's captain insisted his crew did everything possible to stop Vanis, Barezz implied that the loyalty of the Star Destroyer's personnel would be closely examined during their formal assessment.
Shortly afterward, Barezz received information from Skorr, a bounty hunter, that another bounty hunter, Sammie Staable, planned to join the Alliance on Ord Mantell. As Barezz traveled to the planet, Skorr led a team of bounty hunters, including Zuckuss, 4-LOM, and Furlag, to capture Staable and her companions—Raal Yorta, a gambler, and Smileredon-Verdont, a Squib—in a docking bay. Upon arriving, Skorr discovered Raleigh Dawn, a bounty he had previously attempted to collect, in the docking bay. Dawn then boarded Yorta's ship, and the four fled the planet. When Barezz arrived at the docking bay aboard a Chariot LAV, Skorr presented him with a witness: a freighter captain who Dawn had originally hired to transport her off-planet before she escaped with Yorta, Staable, and Smileredon-Verdont. Taking his prisoner to an Imperial-controlled tower, Barezz interrogated the captain using an IT-O Interrogator and learned that he had been hired to take Dawn to a rendezvous, the coordinates of which were on a datapad she had accidentally left on his ship. Despite the captain's claims of innocence, stating he was unaware Dawn was a wanted fugitive and Rebel, Barezz doubted him and ordered his execution shortly after.
After contacting Lord Vader, Barezz relayed his belief that Vanis was gathering more Rebels and that Dawn and Staable were among his recruits. Vader granted the officer full authority to use any necessary forces to capture Vanis. Using the coordinates from Dawn's datapad, Barezz ordered the Aggressor to Bothawui, where he located his targets aboard a relay station in orbit. Barezz ordered the Aggressor to target Yorta's ship, which was docked at the station, destroying it with the Star Destroyer's turbolasers. Using a Lambda-class T-4a shuttle with twelve stormtroopers, Barezz planned to board the relay station and capture the Rebels. However, the four fugitives used an escape pod to reach the surface before heading to Mesa 291, an abandoned lidium mine. Barezz ordered the shuttle to pursue, requesting TIE fighter cover from the Aggressor in case of Rebel intervention, and landed on top of the mining facility. Deploying stormtroopers throughout the facility, Barezz ordered them to capture the Rebels alive so he could interrogate them and discover the location of the hidden Rebel base Vanis intended to take them to. Locating the foreman's office, Barezz used the comm system to demand the Rebels' surrender, which they refused.
The new Rebels fought through the facility until they reached the main shaft, a massive cylindrical chamber with plasma fire burning below and multiple openings along the walls, but no walkways to cross. The Rebels, located at opening 7A on level seven, needed to reach the opposite side of the shaft and descend to opening 6B on level six to reach the hangar where their escape craft awaited. Barezz, unaware of their plan, believed they were attempting to hide deeper within the facility. They intended to use R2-D0, Vanis's astromech droid who he had left to guide his recruits, to bridge the gap using his in-built thrusters with a rope attached. Smileredon-Verdont, riding on the droid, would tie it off at the other end, allowing the Rebels to reach their destination.

Accompanied by three stormtroopers, Barezz entered the shaft at opening 8B on level eight, positioning himself above and opposite the Rebels. The officer ordered his soldiers to open fire; their initial shots struck R2-D0 mid-air, causing him to short circuit and stall. R2-D0 became dead weight, forcing Staable to hold onto the rope to prevent the droid and Squib from falling into the plasma fire. While Yorta secured the rope to help Staable, and Dawn provided covering fire, Smileredon-Verdont tinkered with the droid, reactivating his systems and propelling him toward opening 6B. With the line now taut, Staable was pulled out of the opening and left dangling over the flaming pit. Yorta, using his skills as a former smashball player, threw a thermal detonator up to the level where Barezz and his men were. As one of the stormtroopers caught the device, Barezz began running to escape the impending explosion. The resulting blast gave the Rebels the time they needed to escape, rendezvous with Vanis, and leave the planet.
Barezz's detailed reports on Vanis enabled Ref Mawber, a fellow Imperial Security Bureau officer and friend of Barezz, to identify the Rebel when he landed on Questal. Mawber informed Bandor, the local Moff, and Vanis was subsequently captured while attempting to break into the Moff's palace.
Mar Barezz, a grim and heartless individual, was a devoted follower of the New Order. A staunch supporter of Emperor Palpatine, he believed the Empire represented order and the Rebellion fostered chaos. Barezz also believed the Rebellion was destined to fail. He excelled at uncovering potential spies and traitors within the Empire and the wider galaxy and readily suggested Imperial soldiers be sacrificed if the risk of their defection was high, even without concrete evidence. Mere association with someone known to sympathize with the Rebels was sufficient cause. His pursuit of Alliance agent Tay Vanis became well-known, and Barezz frequently reminded military officers that Lord Darth Vader had personally charged him with capturing traitors and spies. Although officially a civilian without military rank, Barezz often interfered in military matters, such as at Picutorion and during the attempted capture of Tay Vanis, where he criticized the crew of the Star Destroyer Aggressor for failing to capture the spy's X-wing. He was not averse to implying the Star Destroyer crew's loyalty was questionable when they failed to achieve his assigned objective, and he believed his opinion on their performance carried significant weight.

Barezz had little respect for bounty hunters but was surprised when Skorr remained on the scene despite failing to capture the suspected Rebels on Ord Mantell. When the bounty hunter presented him with a witness, the officer ruthlessly interrogated and ultimately killed the prisoner after extracting all available information. He promised Skorr generous compensation if the information proved valuable. Despite being a civilian, Barezz was a capable leader, ordering a precise strike against Raal Yorta's ship instead of destroying the entire relay station, as he aimed to capture the Rebels to locate the hidden Rebel base they were heading toward. He personally led the mission to capture the Rebels at Mesa 291.
Barezz was proficient in wearing light, medium, or heavy armor. He was trained in computer use and skilled in gathering information, interrogation, and intimidation. Barezz could sense when someone concealed their true intentions and possessed extensive knowledge of the New Order, including its protocols and policies.
Barezz wore a standard Imperial Security Bureau uniform and occasionally a fur-collared cloak. He carried a blaster pistol and was trained in its use, along with blaster rifles and heavy weapons. He also carried a vibrodagger and was proficient in its use, as well as a comlink, code cylinder, and datapad.
Mar Barezz made his debut as the primary antagonist in "Rebel Breakout," the inaugural adventure scenario published in the first edition of Star Wars: The Roleplaying Game by West End Games in 1987. He was subsequently mentioned in the Imperial Sourcebook of 1989 within the Imperial Security Bureau entry and appeared in the brief narrative "Picutorion Viewed From the Top." Barezz's entries remained when the book was reprinted in 1994, updated for the Second Edition rules of the roleplaying game. In 1990, Barezz was briefly mentioned in The Game Chambers of Questal, an adventure book for the roleplaying game that was reprinted in 1998 as part of Classic Adventures: Volume Five. The Rebellion Era Sourcebook from 2001 by Wizards of the Coast provided game statistics for Barezz. In 2006, Barezz served as the main antagonist in two webstrips published on StarWars.com, written and illustrated by Pablo Hidalgo—Rookies: Rendezvous and Rookies: No Turning Back. The latter strip was an adaptation of the events of the adventure "Rebel Breakout." Barezz received an entry in The Complete Star Wars Encyclopedia of 2008.
Hidalgo's Rookies webstrips included endnotes. In one, he mentioned basing Barezz's uniform on a rarely used design from the Death Star Technical Companion and that he later wore a fur-lined cloak similar to Admiral Amise Griff's in the Star Wars comic strips by Archie Goodwin and Al Williamson. "Rebel Breakout" does not specify Barezz's fate, implying he survived the encounter in the main shaft to pursue the Rebels to their escape craft. However, Hidalgo had always believed Barezz died at Mesa 291, and the mentions of the officer in the Imperial Sourcebook occurred earlier in his career. This is supported by Jason Fry's establishment of the Battle of Picutorion as part of the history of Beilert Valance, a bounty hunter who first appeared in Star Wars (1977) 16, which was set after the Battle of Yavin, indicating Picutorion occurred before 0 BBY. Additionally, the first edition of The Roleplaying Game suggests "Rebel Breakout" is set after Star Wars: Episode IV A New Hope, as the book frequently references Luke Skywalker as an active Alliance operative. Hidalgo scripted No Turning Back to place Barezz near a thermal detonator explosion, hinting at his fate. However, in his endnotes, Hidalgo stated that Barezz may have survived the explosion. Due to the ambiguity, this article does not definitively state whether Barezz died in the encounter.