Kaesha was born in 18 BBY directly following the end of the Clone Wars. Her clan, supporters of house Kryze, were heavily scrutinized by both the Empire and Clan Saxon. Developing force-sensitive traits at an early age, her parents elected to conceal Kaesha's condition with the aid of an extremely rare and expensive creature known as a Ysalamir. Kaesha would come to know her ever-present pet as "Izzy" as she grew into her adolescence.

In her early teens, Kaesha was relocated to her family's estate on Concord Dawn. Her parents, still loyal to Bo-Katan Kryze, participated in the Rebellion of Mandalore, eventually pushing the Empire off of the world. When the Empire returned, perpetrating the Night of a Thousand Tears, her parents and all of their retainers were killed. Bo-Katan, who managed to survive the initial scouring though mortally wounded, bequeathed the Darksaber to clan Fulrau as caretaker and kingmaker.

Kaesha, too young to accept the responsibility, interred the weapon with Kryze in her hidden tomb within the former Fulrau estate. Following this, Fulrau returned to Concord Dawn, eventually growing into her mother's armor. She hunted the vast wastes of the barren world, surviving alone for many years, trying to draw clanless Mandalorians to her cause with little avail.

Late in 3ABY, Kaesha encountered the rebel Black Squadron while preparing to reclaim a large vein of Beskar from the insidious clan Saxon. Recruiting them to her cause, Kaesha promised a portion of the reclaimed Beskar to Edyssian Bgess. Conducting a raid on the Saxon camp, the Squadron drove the Saxons away, parlaying with their leader Sczier Saxon, whom utilized the opportunity to elevate herself to control of the clan.

Dami Crik, a member of Black Squadron would be heavily wounded in the attack, drawing Kaesha's attention. The two would, eventually, become romantically involved before Crik's mental decline and death in the final days of the war.

Fulrau would, in the interim, travel alongside Black Squadron throughout the last year of the war. During the events of Operation Cinder, Concord Dawn would be subject to a second scouring, reducing the total population of all Mandalorians to less than ten thousand souls. Heartbroken and furious, Fulrau would travel alongside Edyssian to the moon, contesting against the Saxons in a bid for control of the remaining Mandalorians.

Revealing her knowledge of the Darksaber's hiding place, Bgess and Fulrau would return to Mandalore to claim the blade, only to be ambushed by the Saxons while attempting to exit. Losing possession of the sacred blade, the Saxons would bring the weapon of Mandalore to Sczier, who prepared to take control of her people with the intent of joining with the failing Empire.

Fulrau would watch from the sidelines as Edyssian leveled, then emerged victorious from his challenge for possession of the Darksaber, killing Sczier and banishing the remaining Saxons (whom fled to the Imperial side).

Declaring himself as Mandalore the Reckoning and heralding a new crusade against the remaining Imperial states, Kaesha would kneel before Mandalore, becoming a trusted councilor at his side. Often disagreeing with Mandalore's other trusted advisor, Petros Admassu, Kaesha would be a cooling voice to her new overlord.

In the waning days of the war, Black Squadron would initiate a desperate raid to prevent the utilization of the Eclipse against Republic forces at Prakith. Following her liege's instructions, Kaesha would board the super-weapon and carve her way to the drive control room. Mandalore's intention was clear and subverted the desires of the Republic: Take control of the Eclipse and immediately utilize the weapon against the Imperial fleet.

During this final struggle, Kaesha would be overcome by the dark power of the Shadow, massacring dozens of Imperial prisoners before returning to her senses. Rendezvousing with Mandalore and Petros Admassu, the three Mandalorians traveled with the Eclipse as it delved deep into the unknown regions.

Conducting a war of attrition against the thralls of the Shadow, Fulrau would eventually strike the death blow against the possessed form of Dami Crik, which the shadow inhabited.

An uncertain time later, Mandalore would establish the colony of New Mandalore, beginning to manufacture new Beskar armor and rebuild his forces. Utilizing captured Imperial starships, Mandalore would dispatch Kaesha to Ruusar to bolster his efforts on New Mandalore.