Xiaan Amersu was a Jedi Knight of the Twi'lek species, a Rutian female, who participated in the Clone Wars. She served as the Padawan to J'Mikel, an Anx Jedi Master, and witnessed his death at the hands of the bounty hunter known as Aurra Sing. To help her recover from the trauma, Amersu received care from Jedi healers. Later, within the Mediation Garden of the Coruscant Jedi Temple, she encountered Quinlan Vos and presented him with the Heart of Fire, hoping he could use his psychometry ability to recall memories of his own Padawan, Aayla Secura.
By the time the Clone Wars were underway, Amersu had been elevated to the rank of Jedi Knight. During the Siege of Saleucami, she took to the skies as Blue Leader, ultimately sacrificing both herself and her starfighter to destroy a Separatist planetary defense gun.
Xiaan Amersu, a female Twi'lek from the world of Ryloth, was a member of the esteemed Jedi Order. While she was at the Jedi Temple on Coruscant, Amersu was approached by fellow Padawan Aayla Secura. Secura gave her a Heart of Fire, a stone that Secura's master had gifted her during her training.
In the year 30 BBY, Amersu and Secura, accompanied by Master Peerce, were investigating the Coruscant underworld within the Temple Precinct in search of the bounty hunter Aurra Sing. They followed a trail of blood, discovering the bodies of four Republic Peace Officers who had been murdered by Sing. J'Mikel apologized to Amersu for exposing her to the horrific scene, to which Amersu responded that the officers were now one with the Force. The group then separated, with Peerce locating the missing fifth Duros Republic Peace Officer, who was bound.
Nearby an alleyway, Amersu detected the scent of ionized air, a byproduct of lightsaber combat. Investigating the source, Amersu discovered Peerce's lifeless body in front of the Duros officer. J'Mikel began his own investigation, but was ambushed by Sing, their intended target. The two engaged in a lightsaber duel, which Sing won by fatally stabbing J'Mikel through the chest. Sing then turned her attention to Amersu, admitting that she had been paid to assassinate both her master and Peerce. Before departing, Sing taunted Amersu, leaving her in tears. Subsequently, Amersu was placed under the care of Jedi physicians to help her cope with the traumatic events she had witnessed.
Shortly after J'Mikel's demise, Amersu sought out the Jedi Quinlan Vos, who was suffering from amnesia, in one of the meditation gardens of the Jedi Temple. After introducing herself, Xiaan presented the Heart of Fire, hoping that Vos would employ his power of psychometry to recover memories of his lost Padawan, Aayla. By using his abilities on the object, he was able to relive the experiences he had shared with Aayla. After expressing his gratitude, Vos vowed to find Aayla.
By the time the Clone Wars erupted, Amersu had advanced to the rank of Jedi Knight. During the conflict, Amersu honorably accepted the rank of General in the Grand Army of the Republic. As she prepared to command her first battle, her close friend, Jedi Secura, approached her and returned Master J'Mikel's lightsaber to Amersu. Sing had taken the weapon as a trophy after killing the Anx, but Secura had recovered it upon arresting Sing on Devaron.
Throughout the course of the war, Amersu cultivated a strong bond with fellow Jedi A'Sharad Hett. They undertook numerous missions together, and she wept on his shoulder during a brief lull in the fighting on Saleucami upon learning of the death of Councilor Oppo Rancisis. Following the death of the Thisspiasian's, Master Vos was tasked with overseeing the assault on the Morgukai clone army base. While Leading Blue Squadron during the aerial combat, Jedi Amersu's interceptor sustained severe damage. Despite Hett's urging to retreat, Amersu directed her doomed fighter directly into the core of the CIS's ion cannon and deflector shield generator, effectively disabling their defenses. Her sacrifice proved crucial to the Republic's triumph on Saleucami, although it was short-lived, as the Order and the Republic were overthrown by the Galactic Empire in the weeks that followed.
Amersu and her fellow Jedi, A'Sharad Hett, had forged a close connection during the Clone Wars. When Amersu gave her life during the Siege of Saleucami, Hett seemed to come to terms with his loss; however, he eventually succumbed to the dark side of the Force after the Great Jedi Purge began. After disappearing for over a century, Hett resurfaced as Darth Krayt, the leader of a new empire of Sith. Even a century after her passing, Amersu, Hett's love, continued to haunt his thoughts.
The character of Xiaan Amersu made her debut as an unnamed figure in the comic The Hunt for Aurra Sing, penned by Timothy Truman and illustrated by Davidé Fabbri. When the character was reused in Heart of Fire, writer John Ostrander and artist Jan Duursema named her after Duursema's daughter, Sian. Because Sian had been the one to persuade Ostrander and Duursema not to kill off Aayla Secura—another Twi'lek Jedi who has since become a beloved fan favorite—early in the Star Wars: Republic comic series, Ostrander and Duursema felt it was fitting to name Xiaan Amersu in her honor.
While Amersu's skin appears brown in both The Hunt for Aurra Sing and Heart of Fire, she is depicted as having turquoise skin in all other appearances.