The Relentless, a Pellaeon-class Star Destroyer, functioned as the flagship for Darth Krayt's Outer Rim Third Fleet. This occurred seven years following the Dark Lord of the Sith's deposition of Galactic Emperor Roan Fel at the conclusion of the Empire's conflict with the Galactic Alliance. The fleet, led by Kel Dor Admiral Sha Dun, was assigned the mission of capturing Admiral Gar Stazi, who commanded the Galactic Alliance Core Fleet, and obliterating the unified remnants of the Alliance military.
Despite achieving several minor victories, Dun was unable to prevent Stazi's assaults. Consequently, Darth Azard, the Sith Lord overseeing the Third Fleet, executed him on the Relentless's command deck for his shortcomings. Dru Valan, an Admiral with Humanocentric views, replaced Dun. Under Valan's leadership, the Relentless engaged in further battles against Alliance forces above the planet Dac. The battle above Dac culminated in another defeat against Stazi, and the Alliance forces seized the Advanced Star Destroyer Imperious, which was in the process of being built at the planet's shipyards. Although the Relentless survived, the Third Fleet was heavily damaged. Humiliated, Valan relinquished command of the Relentless to Captain Hoge, the vessel's leader, and retreated to his private quarters to contemplate suicide.
Following Darth Wyyrlok's directive to enact the Final Protocol, a scheme involving the poisoning of Dac's oceans and the extermination of its inhabitants within a week, the Relentless and the Outer Rim Third Fleet, now under the command of Admiral Krion Grail, were dispatched to thwart the Alliance's rescue operation on the planet. With Moff Geist and Darth Stryfe supervising the mission, the Third Fleet clashed with Admiral Stazi's forces until a fleet loyal to the exiled Emperor Roan Fel arrived to support the Alliance, forcing Stryfe to withdraw.
The Pellaeon-class Star Destroyer Relentless represented a class of ship initially produced by Kuat Drive Yards for the Fel Empire. The ship's design took inspiration from the wedge shape that was a signature of previous Star Destroyers, and included a heavily angled forward hull. In terms of offense, the Relentless was equipped with turbolasers and a complement of Predator-class fighters. Additionally, the Star Destroyer had shields, a hyperdrive system, and sensor arrays.
Similar to earlier Star Destroyers, the bridge of the Relentless had a command walkway in the middle of the command deck, with crew pits situated on each side. The vessel's commander could view the battlefield through the Star Destroyer's convex arrangement of tetragonal viewports.
In the year 137 ABY, which was seven years after Darth Krayt, the Dark Lord of the Sith, had deposed Roan Fel, the Galactic Emperor, and established his Sith regime at the end of the Empire's war against the Galactic Alliance, the Relentless, a Pellaeon-class Star Destroyer, served as the flagship of Krayt's Outer Rim Third Fleet. The Outer Rim Third Fleet of the Empire, overseen by Darth Azard, a Sith Lord of the Quarren species, was tasked with capturing Gar Stazi, the fugitive Admiral commanding the Galactic Alliance Core Fleet, and destroying the remaining unified segments of the Alliance military, which were called the Galactic Alliance Remnant. Emperor Krayt placed Sha Dun, a Kel Dor Admiral, in command of this mission, and the Relentless and the Third Fleet secured several minor victories against Stazi and the Alliance Core Fleet under his direction.
Despite these numerous small victories, Dun was unsuccessful in stopping Stazi's attacks. Lord Azard executed Admiral Dun for his failure on the command deck of the Relentless, which was stationed in the Calamari sector at the time, and replaced him with Dru Valan, an Admiral who was Humanocentric and had previously encountered Stazi during the Battle of Caamas, the final significant battle of the Sith–Imperial War. Azard cautioned Valan against underestimating Stazi, as Sha Dun had done, and warned the admiral not to fail him. Valan's first action as commander of the fleet was to have Hoge, the Relentless's captain, replace all alien personnel in the fleet with Human personnel.
Admiral Valan devised a plan to trap Stazi by using the potential capture of the Imperious, an Advanced Star Destroyer under construction in the shipyards of the planet Dac, as bait. Niffla, a Toydarian information broker, informed Valan aboard the Relentless that she had seen Monia Gahan, a member of Rogue Squadron and the niece of Gial Gahan, a former Triumvir of the Galactic Alliance, at the shipyards, indicating that Stazi had taken the bait. Stazi's fleet jumped into the system several days later to seize the Imperious, and Valan put his trap into action. Valan arrived in the Calamari system with the Relentless and the Third Fleet, believing he had Stazi's fleet cornered between his fleet and the shipyards. However, Stazi had anticipated Valan's trap and set his own with the help of the Mon Calamari.
Valan and Hoge oversaw the battle from the bridge of the Relentless and watched as Stazi's fleet attacked. Valan ordered the shipyard's automated defense systems to activate and fire on the Alliance ships as a result. However, the Alliance had taken control of the shipyard's defense systems, and sustained fire from both the shipyard and the Alliance fleet reduced the Relentless's shield strength to as low as twenty percent. After Stazi moved his fleet behind the shipyards, Valan ordered the Relentless and the other vessels in the fleet to launch their Predator-class starfighters. Valan, believing one dock to be expendable, ordered his fleet to fire through the shipyard dock that concealed Stazi's flagship, the Scythe-class battle cruiser Indomitable, as the rest of the Alliance fleet escaped.
The Alliance seized the Imperious and destroyed a third of the shipyards. Although the Relentless remained intact after the battle, Valan's fleet was devastated, and Stazi escaped once more. Humiliated, Valan relinquished command of the Relentless to Captain Hoge and retreated to his quarters to contemplate suicide rather than face Darth Azard.
Following Darth Wyyrlok's order to implement the Final Protocol, a plan that involved poisoning the oceans of Dac, the homeworld of the Mon Calamari, and executing all of its inhabitants within a week, the Relentless, along with the remainder of the Outer Rim Third Fleet, was being overseen by Darth Stryfe. Knowing that Admiral Stazi would return to rescue the inhabitants of Dac, the Outer Rim Third Fleet, now under the command of Admiral Krion Grail and Geist, a Moff, was dispatched to ensure the failure of the rescue effort.
The Third Fleet entered the system ten hours into the Alliance rescue operation and engaged Stazi's forces. Despite the Sith fleet's numerical superiority, Stazi used ion bombs loaded onto drone ships to eliminate a significant portion of the Third Fleet. When the Relentless and the other Imperial vessels destroyed the drones, they released an ion charge that damaged the ships' sensors, enabling the Alliance to attack while the Sith fleet was temporarily disabled. The Relentless narrowly avoided destruction, and Stryfe ordered Grail to target the first wave of refugee ships as they attempted to leave the system.
While the Sith attacked Stazi's flagship, which was protecting the refugee ships, a fleet loyal to Roan Fel's Empire-in-exile, the former Emperor, entered the system to aid in the evacuation of Dac and engaged Stryfe's forces. Geist persuaded Stryfe to withdraw their remaining ships, knowing that the Relentless could not continue the attack without being destroyed. The Alliance and Imperial forces were able to evacuate twenty percent of the planet's population, now unhindered by the Sith fleet.
As the flagship of the Outer Rim Third Fleet, the Relentless was under the overall command of Admiral Sha Dun, a Kel Dor, during the mission to eliminate Alliance admiral Gar Stazi. After Darth Azard killed Dun for failing to stop Stazi, the Relentless and the Third Fleet came under the overall command of Dru Valan, a Human Admiral who practiced speciesism. Captain Hoge, who served under both Dun and Valan, directly commanded the vessel itself. Valan relinquished command of the Relentless's bridge to Captain Hoge following the battle with Stazi's fleet at Dac. Later, during the evacuation of Dac, the Relentless remained the flagship of the Third Fleet and was under the overall command of Admiral Krion Grail.
Under Dun's command, the crews of both the Relentless and the other vessels of the Third Fleet consisted of members of various species. However, Valan ordered Captain Hoge to replace all alien personnel in the fleet with Human personnel as his first act in command.
The Relentless was first seen in the twentieth issue of the Star Wars: Legacy series, titled Indomitable, Part 1, which was released on February 27, 2008. John Ostrander wrote the issue, and Omar Francia provided the pencils.