Sarro Xaj, a human male Jedi Knight of considerable size, lived during the era known as the Golden Age of the Old Republic. He studied under the tutelage of Master Raskta Lsu, and fought alongside her during the New Sith Wars on the planet Ruusan. Around 997 BBY, he achieved the rank of Jedi Knight and, emulating his master, pursued the path to becoming a Jedi Weapon Master.
Xaj accompanied Raskta Lsu, Worror Dowmat, Valenthyne Farfalla, and Johun Othone aboard the Justice Crusader to Tython, with the goal of confronting the Sith Lord Darth Bane and his apprentice, Zannah. Upon their arrival at Belia Darzu's castle, they immediately engaged Darth Bane and Darth Zannah in a duel.
Xaj fought with a blue double-bladed lightsaber that was almost three meters in length and, together with fellow Jedi Othone, attacked Zannah. However, Othone's inexperience hampered Xaj's efforts. Xaj's offensive was disrupted by Othone's clumsy strikes, forcing Xaj to restrain his attacks to avoid harming his ally. At one point, Farfalla requested assistance, and Xaj yelled at Othone to aid him, leaving Xaj to fight Zannah alone. With the aid of the Force channeled through him by Worror's battle meditation, Xaj gained the upper hand over Zannah in their individual fight. He used his superior strength to wear down his opponent, forcing her into a corner. As he prepared to deliver the finishing blow, Worror's concentration faltered, cutting off the battle meditation and depriving Xaj of the power provided by the Ithorian Jedi Master. Xaj paused and looked towards his companions to understand what had occurred. Taking advantage of this hesitation, Zannah attacked Xaj's mind with Sith sorcery and then killed him with a strike to his chest.
Following his demise on Tython, the Jedi High Council, having been informed of Darth Bane's existence by Caleb of Ambria, dispatched a team of Jedi, including Masters Tho'natu and Obba, to eliminate him. On Ambria, within Caleb's encampment, the Jedi discovered the lightsaber hilts of the fallen Jedi, including Xaj's. Upon the team's arrival, they were attacked by a crazed Darovit, whom they believed to be Bane suffering from the effects of the orbalisk armor. After killing him, they declared the Sith extinct and returned the lightsaber hilts to the Temple.
Upon their return to the Temple, the Jedi created a memorial honoring those Jedi who contributed to the destruction of the Sith. The lightsaber hilts of all five Jedi were embedded within a large white stone block located in the gardens surrounding the base of the Tower of First Knowledge. Beneath each hilt was a depiction of its owner, accompanied by their name.
Sarro Xaj was a physically imposing individual, standing over two meters in height and weighing 150 kilograms. He possessed olive-brown skin and a single topknot of black hair. Xaj's early passion for lightsaber combat caught the attention of Weapons Master Raskta Lsu. He exuded confidence in his abilities, even joking that the impending battle with the Sith Lords on Tython might prove too easy. He even smiled at Zannah during their duel, once he was able to engage her without Othone's interference.
As a Padawan, Xaj chose to emulate his master by striving to perfect his lightsaber skills. He accompanied his master during the Ruusan campaign, and a few years following the New Sith Wars, Lsu concluded his training, deeming him worthy of the rank of Jedi Knight. He eventually attained the rank of Weapons Master. His proficiency with a double-bladed lightsaber was sufficient to overwhelm Darth Zannah in single combat with the assistance of Worror's battle meditation. Zannah noted that Xaj's fighting style displayed greater refinement than Bane's. However, once the effects of the meditation ceased, his distraction left him vulnerable to Zannah's Sith sorcery, leading to his death.