Dark forces combined to bring her under the sway of the zerg Overmind, but the same courage and tenacity that she had shown as a ghost, and later as a rebel against the Confederacy, brought about her dominance of the alien sentient. Now she holds the reins of the Swarm and commands an innumerable army of monstrous creatures poised to sweep mankind from the Koprulu sector.
Sarah Louise Kerrigan discovered the strength of her latent psionic gift as a young girl. An innocent flash of childish anger at her parents resulted in massive cerebral hemorrhaging and a horrific death for her mother. Her father would only repeat one thing over and over again in the ensuing years: “I saw her head come apart.” This gruesome event alerted the Terran Confederacy to her powers, and she quickly became the focus of the fledgling ghost program. Because she had reached unheard-of scores on psi-evaluation tests, her abilities elicited a complete readjustment of the scoring system so that she could be properly measured. The remnants of her humanity were stripped from her, and Kerrigan was designated Ghost Number 24601.
Following her emergence from the ghost program, she became an unstoppable assassin for the corrupt Confederate government. It was her assassination of the independent senator Angus Mengsk that brought her to the attention of his ambitious son, Arcturus. At first wishing to extract revenge from Kerrigan for his father’s murder, Arcturus soon realized that she was much more useful as a weapon against the Confederacy. After rescuing her from a clandestine experimental facility, he removed her neural inhibitor and used her restored memories to build righteous anger against the government that had abused her. Kerrigan and Mengsk became allies.
She was running a mission on Antiga Prime when she first came across one-time Confederate marshal Jim Raynor, a new recruit to the Sons of Korhal. He disapproved of her lethal dealings with the Confederacy, but the conflict between the two soon grew into mutual respect, admiration, and even… something more. Kerrigan and Raynor ran several secret missions together before Mengsk’s revolutionary movement brought them to Tarsonis. Even Kerrigan’s jaded sensibilities were shocked when she learned what Arcturus had planned for the Confederate capital world: the placement of psi emitters to lure the zerg to one of the most densely populated planets in the sector. It would result in the death of almost every living thing on Tarsonis. Voicing her opposition, she nonetheless set about loyally fulfilling her mission to protect the hive clusters from a mysterious new alien enemy, the protoss. Mengsk would take advantage of that loyalty, abandoning her to die on Tarsonis when the mission was complete. He couldn’t run the risk of having a powerful weapon like Kerrigan running loose in the shadow of his new government, and he couldn’t resist the chance to claim some vengeance long overdue. This betrayal enraged Raynor; he left the revolution, swearing revenge.
Kerrigan was captured by the zerg, and the Overmind—a sentient being who controlled them—saw the destiny of its race intertwined with her potential. She was assimilated into the Swarm; her will left intact. No longer an assassin, nor even human, she became the Queen of Blades.
Soon after her ascension, the death of the Overmind left a power vacuum in the Swarm. The ensuing Brood War saw Kerrigan defeating foe after foe, and she even turned on old allies like Jim Raynor. When the conflict ended, she was in full control of the zerg.
Or so she believed, for a dark influence, with twisted plans for the zerg and the galaxy, crept into her thoughts, exerting its will through her zerg mutagens—Kerrigan could not resist. She quietly prepared the Swarm until the Dark Voice commanded her to claim a powerful xel'naga artifact. She obeyed.
But Jim Raynor was a step ahead of her. Kerrigan’s old friend and his Raiders assembled the artifact and used it in an attempt to save her—stripping the Queen of the zerg mutagens and the Dark Voice. Raynor had put aside his anger in the hopes of saving the woman he had once known.
For a time, Kerrigan didn't believe she was worth saving. Guilt over her actions haunted her, but that guilt turned to anger when Arcturus Mengsk launched an attack that led to Jim Raynor's capture… and apparent execution. Enraged, Kerrigan sought to bring Mengsk down for good. She needed allies; few terrans would help her.
Thus she turned to the zerg. Brood by brood she reassembled her old Swarm, and became the Queen of Blades once again. She hoped that the Dark Voice would find no grip on her mind.
While Kerrigan dismantled Mengsk's armies and laid siege to critical facilities, she made a startling discovery: Jim Raynor was alive. Unfortunately, Raynor was furious to discover Kerrigan’s choice, but eventually agreed to help her.
The reunited Swarm and its human allies toppled Mengsk's elite troops, and cornered him in his palace. The emperor's final act—trying to kill Kerrigan with the xel'naga artifact—failed thanks to Raynor's intervention. Kerrigan finally exacted her revenge, killing Arcturus Mengsk.
Now Kerrigan prepares for what lies ahead. Though one enemy is dead, another remains: the Dark Voice that once controlled her. This is the one true threat left in the galaxy.
And it is her next target.