During a raid on a remote Terran outpost, Arcturus Mengsk discovered and rescued Kerrigan from the Confederate scientists. The Confederates had ruined both their lives, and it was a simple matter to convince the young woman to lend her formidable combat skills to his rebel strike-force: The Sons of Korhal.
After faithfully serving the Sons of Korhal for years, Kerrigan was abandoned by the power-mad Mengsk, and left for dead upon the Zerg-infested world of Tarsonis. The Zerg Overmind, sensing tremendous psychic potential and an indomitable will within Kerrigan, decided to incorporate her into the Swarm. Kerrigan's genes were spliced with those of the Zerg, transforming her into the terrible Queen of Blades. Kerrigan's latent psychic powers manifested themselves rapidly, allowing her to lead the Zerg to countless victories over their enemies.
"Behold the power of that which is yet unborn! For the swirling images that flow forth from the Chrysalis are only a shadow of the sleeper's true power."
--Kerrigan Queen of Blades
After the Overmind was destroyed by the Protoss hero, Tassadar, on the planet Aiur, Kerrigan began to bend the scattered Zerg Broods to her will. Opposed only by the Renegade Cerebrates led by Daggoth, Kerrigan hoped to gain mastery over the entirety of the Zerg Swarm.
(description from www.blizzard.com)
