Little is known of Kleya's early life; her family, friends, and home-planet are left nameless. Even her name "Kleya Marki" is only an alias. All that is known is that when she was a young girl, the Empire attacked and massacred her people, mercilessly killing men, women, and children. Kleya only escaped the same fate due to the intervention of one of the commanding officers of the massacre, a man known as Sergeant Lear. Horrified at his complicity in the massacre, Lear fled on his ship with Kleya to start a new life as fugitives from the Empire. At Lear's side, Kleya grew to be resourceful, strong-willed, and utterly dedicated to the cause of defeating the Empire and its operatives. Together, she and Lear created a false life with Lear taking on the name of "Luthen Rael" and cultivating a persona of an eccentric antiques' dealer, with Kleya acting as his dutiful, charming assistant. All the while, the two secretly commandeered a Rebel cell of spies and saboteurs, working in the heart of Coruscant to bring down the Imperial regime.

Kleya's most defining trait is that she is driven—driven by grief, by rage, by a ruthless mission to end the Empire that destroyed her home. Even as a child, she was consumed by her desire for revenge and would intentionally put herself in the position to witness ever more of the Empire's atrocities, intentionally feeding her own hate to fuel her mission. She yearned to strike back against the Empire, but under Luthen, would learn patience, subterfuge, and restraint, spending years cultivating the perfect opportunity to bring the Empire to its knees. In public, Kleya conceals this fervor under the guise of being nothing more than Luthen Rael's charming and congenial assistant. Though she plays her part perfectly, her true demeanor is a far cry from her mask. She is often cold, acerbic, and ruthlessly utilitarian; as someone who lives and breathes for the cause, she expects the same level of devotion from others, and shows little sympathy for those who falter. Yet, underlying this seeming callousness is a deep sense of horror at the harm the Empire inflicts on innocent people, and a desire to see its end at any cost.

Kleya is highly adept at subterfuge, able to slip in and out of a variety of unassuming roles at a moment's notice. She is also a capable engineer, using jury-rigged radios and listening devices to spy on persons of interest and coordinate her and Luthen's network of Rebel operatives. Finally, Kleya is skilled with a blaster and explosives, acting as a one-woman assault team when the situation calls for it.