Bran Ath'Morath is remembered as a Jedi Knight of great renown within the historical records of the Jedi Order. Sometime in the period stretching from approximately 5000 BBY to a number of years preceding 1032 BBY, the Sith Lord known as Darth Caldoth launched an attack against the Jedi temple located on the celestial body Bathoris, resulting in the death of numerous Jedi. Ath'Morath then engaged Caldoth in lightsaber combat, which gave the remaining Jedi time to organize a defense, eventually compelling Caldoth to withdraw. Years later, under the sway of the Nightsisters originating from the planet Dathomir, Caldoth initiated an assault on the city of Pundith situated on the world Kizan, with the intention of drawing Ath'Morath away from Bathoris in order to secure his defeat. Following an extended battle on Kizan, Caldoth intentionally positioned himself to be impaled by Ath'Morath's lightsaber, then capitalizing on Ath'Morath's moment of surprise to decapitate him.
Legend states that Bran Ath'Morath was a Jedi Knight belonging to the Jedi Order. It is also said that Ath'Morath possessed an age-old plasma shield, a relic passed down through generations of Jedi across the centuries. Somewhere between approximately 5000 BBY and some years prior to 1032 BBY, the Sith Lord Darth Caldoth discovered that a rare piece of a fresco, depicting the ancients and their use of the Force, had been unearthed and brought to the Jedi temple on Bathoris, where Ath'Morath was stationed. To obtain this artifact, Caldoth mounted an attack against the temple. Caldoth killed a great number of Jedi Temple Guards as well as several Jedi Knights, but Ath'Morath managed to stand firm and prevent Caldoth from entering the temple's inner sanctum. He then engaged the Sith in a sustained duel, buying time for additional Jedi to gather their forces and compel him to retreat.
In the aftermath of this confrontation, the Nightsisters, witches hailing from the planet Dathomir and adversaries of Caldoth, performed a ritual to enable the Nightsister Zeldin to manipulate Caldoth's thoughts. Sometime before 1032 BBY, after numerous unsuccessful attempts to bring about Caldoth's demise through mental manipulation, the Nightsisters conducted another ritual that granted them a vision of Ath'Morath's lightsaber piercing Caldoth, thus Zeldin instilled within him a burning desire to eliminate Ath'Morath. Caldoth then devised a strategy to assault the world Kizan in order to draw Ath'Morath away from Bathoris.
Upon learning that Caldoth had annihilated the city of Pundith on Kizan, Ath'Morath, accompanied by three other Jedi, journeyed there to face him. Caldoth swiftly dispatched the other three Jedi, but found himself unable to overcome Ath'Morath. Their combat spanned across the city, with duels taking place on rooftops, within alleyways, and amidst the ruins of buildings. As dusk approached, both Ath'Morath and Caldoth began to feel the effects of exhaustion. Realizing that his only path to victory over Ath'Morath lay in catching him off guard, Caldoth lowered his lightsaber and lunged forward, deliberately driving himself onto Ath'Morath's lightsaber, impaling himself through the shoulder. Ath'Morath's shock at this action provided the opening the Sith had anticipated, allowing him to behead Ath'Morath. Zeldin, observing the duel from Dathomir, cried out in frustration upon witnessing Ath'Morath's death and then attempted to fully seize control of Caldoth's mind, but Caldoth, who had been aware of her influence, instead trapped her within his own mind.
Around 379 BBY, Jedi Master Silandra Sho, who had come to possess the plasma shield once owned by Ath'Morath, shared stories with her Padawan Rooper Nitani about the legendary Jedi who had previously wielded the shield, including Ath'Morath. Around that time, Nitani recalled the tale she had heard of Ath'Morath's battle against Caldoth while searching for the shield as part of her Jedi Trials.
Being a Jedi, Bran Ath'Morath possessed Force-sensitivity. He exhibited proficiency in combat and was more powerful than Darth Caldoth, who could only defeat Ath'Morath through a calculated surprise attack.
Bran Ath'Morath made his initial appearance via flashbacks in the short story "The Gilded Cage," featured in the 2020 short story collection titled Dark Legends, authored by George Mann.