Taken from the Star Wars Wiki

Komari Vosa, a Force-sensitive Human female, was a fallen Jedi who served as leader of the Bando Gora during the final years of the Galactic Republic. A former Padawan of Jedi Master Dooku, who remembered Vosa as an excellent pupil, Vosa ultimately turned to the dark side of the Force following her banishment from the Jedi Order. Amassing an army of mindless slaves and assassins, Vosa became a cult leader whose influence reached across the galaxy, allowing her to establish connections with powerful crime lords such as the Hutt Cartelor the Dugs of Malastare.

As her influence expanded, Vosa came to the attention of Darth Sidious—the Dark Lord of the Sith who conspired to topple the Republic from within. Viewing the former Jedi as a threat to his own plans for the future, the Sith Lord ordered her termination. The execution of this task was entrusted to Sidious' new Sith apprentice, Darth Tyranus, who was in fact Dooku, the Jedi Master that trainedVosa prior to his own experience falling from the light side of the Force. Rather than killing Vosa in person, Tyranus opted to place a bounty on his fallen apprentice. A mercenary who was skilled enough to defeat a warrior trained in the ways of the Force would, as Tyranus reasoned, make an ideal template for the clone army in development on Kamino.

The contest was ultimately won by Jango Fett, one of the bounty hunters whom Tyranus hired to hunt and neutralize Vosa for the reward of five million credits. After tracking Vosa to her citadel on Kohlma, one of the moons of Bogden, Fett defeated the leader of the Bando Gora in spite of her Force powers and lightsaber skills. Tyranus, who witnessed the battle from the shadows, asphyxiated Vosa by way of the Force and subsequently persuaded Fett to be cloned. In the years following Vosa's death, her lightsabers were given to Asajj Ventress, a Separatist assassin who aspired to join the ranks of the Sith with Tyranus as her mentor.

Reclaiming his birthright as Count of Serenno and his vast fortune, Dooku conspired with Sidious to force the galaxy into a war that would bring the Sith to power. He forged ties between corporations and planets discontented with the Republic, and became the leader of the Separatist movement that coalesced into the Confederacy of Independent Systems. Thousands of star systems flocked to Dooku's banner and seceded from the Galactic Republic. Dooku also was tasked by Darth Sidious to recruit a suitable host for their clone army. He set a competition, by marking his former apprentice, Komari Vosa, now turned evil, with a 5 million credit bounty, attracting Bounty Hunters Jango Fett and Montross, with Fett ultimately winning the competition.