Ros Lai's parent was a Jedi Knight during the waning decades of the Galactic Republic. This Jedi found himself captured by the Nightsisters and enslaved by the witch Zalem upon being dispatched to the planet of Dathomir for an assignment. Following procreation, Zalem killed her spouse, a common practice among the Dathomiri witches. Ros Lai, their offspring, was raised with animosity towards her mother, vowing to exact retribution for the demise of her father, whom she had never met.