Komari Vosa was a Jedi padawan under Dooku, then a Jedi Master, shortly before the Clone Wars started. However Vosa was never allowed to rise to master level or knight status because the High Council believed her to be unworthy of such a promotion. This eventually led Vosa to a criminal organization called Bando Gora and the dark side. Komari's fall led her to create a set of unique new lightsabers. These weapons were designed to have curved hilts, like Dooku's weapon, and the ability to link together to form a saberstaff.
After Komari Vosa's death, at the hands of Dooku, the Sith Lord recovered and saved both lightsabers, and so they remained unused for years until the time of the Clone Wars. While searching for a new dark side acolyte, the Count witnessed the strength of Asajj Ventress. After a brief confrontation in which Ventress' old Jedi lightsabers were destroyed, Darth Tyranus rewarded her with this pair of sabers.
Asajj Ventress would use them in nearly all of her fights throughout the entire war, making these lightsabers her signature weapons.