Once known as Agent 5241, Kreel was a human male who served the Galactic Empire as an undercover stormtrooper sergeant and a SCAR trooper. Affiliated with the 501st Legion, he directly answered to Darth Vader. On Nar Shaddaa, he took on the role of gamemaster within Grakkus the Hutt's arena. His responsibilities included the training of arena combatants, one of whom was Luke Skywalker. During Skywalker's confrontation with Kongo the Disemboweler in the arena, Agent 5241 notified the Empire of Skywalker's presence on Nar Shaddaa. Following the completion of his assignment on Nar Shaddaa, Kreel was placed in charge of an elite SCAR trooper unit called Task Force 99.
Kreel was a male human born on the planet Chagar IX. At the age of four, Kreel witnessed a man's death, an event that caused him to weep repeatedly. Two years later, his own father was murdered before his eyes, yet he remained dry-eyed. His mother was also said to have died in the arenas. He subsequently embraced killing as a means of survival, finding work in the fighting pits. These fighting pits became his way of life. Later, upon first seeing the Galactic Empire's stormtroopers, Kreel found them to be a beautiful sight. After the Empire overthrew the warlords of Chagar IX and ended the fighting pits, Kreel and his people were provided with jobs, purpose, and stability. Once he reached adulthood, Kreel enlisted in the Stormtrooper Corps.
He attended the Imperial Academy, where he formed a friendship with Izak Anzio, a ranger from Agamar. During their initial joint mission, Izak lost his life to Rebel mortars before their transport even landed. In response, Kreel eliminated every Rebel he could find that day, vowing to continue his actions. Eventually, Kreel achieved the rank of sergeant within the 501st Legion.

The Sith Lord Darth Vader selected him for a clandestine operation: to infiltrate the palace of Grakkus the Hutt on Nar Shaddaa. He adopted the guise of one of Grakkus's most skilled fighting slaves, purportedly acquired through purchase. In this role, Kreel was responsible for training Wookiees, lizard men, and space pirates for combat in Grakkus's arena, earning the moniker "Gamemaster."
In time, he received Luke Skywalker as a trainee for Grakkus's games. Alongside MagnaGuards, Kreel instructed Skywalker in combat techniques. He engaged in discussions with Grakkus and observed the MagnaGuards' encounters with Skywalker. Subsequently, he was shown the creature that Skywalker would face in the arena. Kreel then escorted Skywalker to the arena for his battle against Kongo the Disemboweler. Shortly thereafter, Kreel contacted a squadron of TIE/ln space superiority starfighters, informing them of Skywalker's presence.

Kreel activated Kongo's shock collar before neutralizing Grakkus's MagnaGuards with a lightsaber. He then placed Grakkus under arrest, declaring the arena's closure. He was supported by several TIE pilots who surrounded Skywalker. However, during the apprehension of Grakkus and Skywalker, Grakkus initiated an E.M.P. that neutralized the weapons of Kreel and the TIE pilots. Kreel then brandished his lightsaber as Kongo regained consciousness. Kreel attempted to restrain Skywalker but was attacked by Grakkus. He commanded the pilots and stormtroopers to capture Skywalker and his allies. Following these events, Kreel spoke with Vader about Skywalker, showcasing Grakkus' collection of Jedi artifacts to the Sith Lord.

Soon after the events on Nar Shaddaa, Kreel was assigned leadership of Task Force 99, a SCAR trooper unit. Kreel and his team journeyed to Sunspot Prison in search of Kolar Ludd. Subsequently, Kreel and his squad received a new mission on the Ghost Moon, where they successfully shot down the Rebels' Taylander shuttle. He and his squad then launched an assault on the rebel forces, with Kreel using his lightsaber to destroy a tank. The attack proved successful, resulting in the capture of Admiral Verette, who was then interrogated.
Kreel then had Verette bound to his shuttle and sent it towards the captured Star Destroyer Harbinger as a diversion, while he and his SCAR troopers boarded the Harbinger to reclaim it. Kreel then engaged in combat and a duel with Skywalker, revealing himself as the Gamemaster from Grakkus's arena. During the battle, Vader contacted Kreel, warning him against harming Skywalker—a communication that allowed Skywalker to sense Vader's presence, causing him to lose focus. Kreel capitalized on Luke's attempt to use the Force, which he dismissed as hindering true combat skill—but before he could fully defeat the young Jedi, Luke unleashed a Force push that shook the entire Star Destroyer, trapping Kreel under wreckage and debris. As Luke and the others escaped, Kreel instructed his team to salvage the mission by destroying the Star Destroyer, while he severed his own arm at the shoulder with his lightsaber, enabling him to rejoin them as they fled the ship. Although Vader was enraged by the complete failure of Kreel and his SCAR team in achieving their objectives, Kreel and Task Force avoided the full force of his anger by presenting a valuable captive: the protocol droid C-3PO.
Kreel and SCAR Squadron brought 3PO to the Devastator, where they attempted to interrogate him in order to uncover the location of the Rebel fleet or any new bases. However, Vader ordered Kreel to eliminate 3PO. Despite these orders, Kreel decided to use 3PO as bait to draw the Rebels to their location.

Later, while Kreel was practicing his lightsaber skills, Vader arrived and expressed his disappointment regarding the events on the Harbinger. Nevertheless, Kreel persuaded Vader to spare him and his squad. Vader then ordered the squad to proceed to the Horox system to eliminate a rebel base. Before their departure, the Emperor arrived, and Kreel knelt in respect. The Emperor instructed him to continue his service, stating that the Empire needed more soldiers like him. He and his squad traveled to the Horox system, where they discovered villagers oppressed by a tyrant, whom they killed, earning the villagers' gratitude. The villagers then provided them with the coordinates of the rebel base. On Horox III, they located and destroyed a rebel base.
Kreel and SCAR Squad later confronted the rebels once more on the planet Crait, where the Rebels were attempting to construct a new base. SCAR Squad engaged the rebel forces on the planet but were defeated. The squad managed to escape; however, Kreel's lightsaber was destroyed during a duel with Skywalker. Despite this setback, Kreel was able to repair his lightsaber and use it again in a skirmish on Hubin.
The reference work Star Wars: The Mini Book of Lightsabers incorrectly asserts that Kreel makes appearances in both Star Wars (2015) and Star Wars (2020), but he is only present in the 2015 series.