Callef was a Human male Dark Jedi who existed during the Cold War era, a period of tension between the Galactic Republic and the reconstituted Sith Empire. Serving as an apprentice to Bengel Morr, Callef, along with his master, incited the indigenous Flesh Raiders of the planet Tython, aiming to bring about the downfall of the Jedi Order. In the initial phases of the Flesh Raider uprising, he commanded his Flesh Raider soldiers in an attack targeting the Jedi base situated within the Tythonian Gnarls, successfully capturing a Bith apprentice named Unaw Aharo. However, Callef met his death in a duel against another Jedi apprentice who had arrived to liberate Aharo.
Callef, a Force-sensitive male Human, became the apprentice of the Dark Jedi known as Bengel Morr at some point prior to 3643 BBY. Morr, a Nautolan who was once the apprentice of Jedi Master Orgus Din, vanished during the Sacking of Coruscant in 3653 BBY carried out by the Sith Empire, subsequently descending into madness over the following ten years. Morr instilled in Callef the belief that the Jedi Order had grown feeble and ineffective, advocating for its destruction and reconstruction into a more formidable entity.
Around the year 3643 BBY, Callef and Morr initiated their assault on the Jedi homeworld of Tython. In their ambition to topple the Jedi Order, he and his master sparked an uprising among the native Flesh Raiders, utilizing these primitive beings as soldiers while orchestrating events from the shadows. Exploiting a concealed passage that linked the Tythos Ridge with the Tythonian Gnarls, Callef spearheaded a Flesh Raider invasion force into the Gnarls, targeting the Jedi's stronghold there. A Bith Jedi apprentice, identified as Unaw Aharo, had detected the increased activity of the Flesh Raiders in the region and relayed his observations to Jedi Master Derrin Weller. However, shortly after transmitting his report, Aharo was apprehended by Callef's forces, who then presented the injured and disarmed Bith to the Dark Jedi within the cave.
Callef commenced questioning Aharo, who was taken aback by the Human's possession of a lightsaber. Nevertheless, a young Padawan disrupted Callef before he could eliminate the Bith, having overcome the Flesh Raider soldiers guarding the cave. The Jedi apprentice's combat prowess piqued the Dark Jedi's interest, but Callef, confident in his own abilities, summoned two Flesh Raider guards and engaged the Padawan. Despite wielding only a vibrosword against the Dark Jedi's lightsaber, the apprentice battled and triumphed over Callef in a duel, resulting in Callef's death.
Following his demise, Master Orgus Din arrived, sealing the cave after retrieving Callef's lightsaber. Remarking on the weapon's peculiar familiarity, Din escorted Aharo to a medcenter and instructed the other Padawan to report to the Jedi Temple. Subsequently, the Padawan was contacted by Callef's master, Bengel Morr, who expressed his disappointment at Callef's easy defeat. However, Morr remained unconcerned, doubting the Padawan's capacity to defeat him and halt the Flesh Raider invasion.
Callef, a Force-sensitive Human male with fair skin, possessed black hair and brown eyes. He was proficient in Basic and capable of understanding the language of the Bith people, as well as the guttural language employed by the Flesh Raiders. Arrogant and cruel, Callef subscribed to the philosophy of survival of the fittest, and he held in contempt what he perceived as the Jedi Order's passivity and weakness. Mirroring his master Bengel Morr, Callef sought the Jedi Order's destruction with the intention of rebuilding it according to their own principles. The Padawan responsible for Callef's death later conveyed to Grand Master Satele Shan that Callef appeared composed—the apprentice detected no anger or fear within the Dark Jedi, despite his utilization of the dark side.
As Bengel Morr's apprentice, Callef brandished a blue-bladed lightsaber modeled after his master's own weapon. Upon recovering Callef's lightsaber from the Dark Jedi's corpse, Orgus Din—Morr's former master—was struck by the weapon's familiarity, although he could not recall its specific origin.
Callef's creation was for Star Wars: The Old Republic, a massively multiplayer online role-playing game launched by BioWare on December 20, 2011. He serves as the initial boss encounter for the Jedi Knight character, as part of the player's introductory class quest titled "Attack of the Flesh Raiders." Players have the option to attack Callef during their conversation to gain dark side points, or to demand Callef's surrender to earn light-side points. Given that the Jedi Knight is a Republic character, it is presumed that the Knight exclusively chooses light-side options. As part of an April Fool's prank in 2011, several cinematics from the game were published on The Old Republic's website featuring vocalizations in Shyriiwook, the language spoken by the Wookiee species. One of these videos depicted the events of the mission "Weapon of the Jedi," in which players confront Bengel Morr; however, the video substituted Callef for Morr.