Kerrigan's Swarm: the Zerg Swarm under the Queen of Blades

Kerrigan's Swarm was the faction of the Zerg Swarm led by Sarah Kerrigan, the Queen of Blades. The zerg were a ruthless amalgamation of biologically advanced aliens dedicated to genetic perfection, named the Swarm for their ability to rapidly create strains and overwhelm their foes. When the first Overmind was slain on Aiur and the zerg were left leaderless, the Swarm split into rival factions, one led by Kerrigan and another, the renegade zerg, led by the cerebrate Daggoth and the growing second Overmind. The broods that Kerrigan brought under her control became her instrument through the Brood War, the Second Great War, and the End War against Amon. (StarCraft; StarCraft: Brood War; StarCraft II: Heart of the Swarm)

Origins in the death of the Overmind#

During the Great War, Sarah Kerrigan was abandoned to the zerg on Tarsonis, taken to Char, and transformed there into the Queen of Blades. The first Overmind intended her to succeed it as the Swarm's leader and free the zerg from the will of Amon. When the Overmind was slain by Tassadar on Aiur, the Swarm was left without a master, and the leaderless zerg fractured. One faction formed around Kerrigan, while another, the renegade zerg, gathered under the cerebrate Daggoth, who initiated the creation of a second Overmind. The split sparked a zerg civil war that ran through the Brood War. (StarCraft; StarCraft II: Heart of the Swarm; StarCraft II: Legacy of the Void)

Mastery of the Swarm in the Brood War#

Kerrigan sought to kill the new Overmind before it could mature and resume control over the whole Swarm, including her. The civil war was complicated by the arrival of the United Earth Directorate Expeditionary Fleet, which overthrew the Terran Dominion, captured the second Overmind, and used the psi disrupter to fragment the zerg opposing it. Kerrigan manipulated anti-UED terrans, including Raynor's Raiders, and the protoss into destroying the psi disrupter, breaking UED control over the sector, and slaying the Overmind. With its death the entire Swarm came under her control. When the alliances of convenience dissolved, Kerrigan turned on her partners; the reformed Dominion, the UED remnants, and the protoss tried and failed to oust her, and the war ended with all sides withdrawing as the zerg held the worlds they had infested. (StarCraft: Brood War)

For the next four years the Swarm avoided outright conflict while slowly expanding and evolving, the remaining cerebrates dying and being replaced by broodmothers. As the first hybrids appeared and signs of Amon's machinations reached Kerrigan, Zeratul discovered that her survival was essential to preventing the Swarm from fulfilling the Dark Voice's apocalyptic plans, and he instructed Jim Raynor to ensure she lived. (StarCraft: The Dark Templar Saga: Shadow Hunters; StarCraft II: Wings of Liberty; StarCraft II: Heart of the Swarm)

The Second Great War and rebirth#

The Second Great War began with the Swarm's invasion of terran space in search of a xel'naga device. Raynor's Raiders, working on behalf of Valerian Mengsk's Moebius Foundation, recovered the device first, and a joint Raider and Dominion force used it on Char to restore Kerrigan to her terran form. The Swarm fragmented in her absence. Doggedly pursued by the Dominion, which captured Raynor and reported his execution, Kerrigan began reuniting the Swarm as a tool of vengeance. (StarCraft II: Wings of Liberty; StarCraft II: Heart of the Swarm)

During this period the Swarm journeyed to Zerus, where it was reunited with the primal zerg and Kerrigan became a primal zerg-human hybrid, a form more powerful than her previous one and free of Amon's influence. The Swarm discovered and destroyed a secret hybrid facility at Skygeirr run by Doctor Emil Narud, a servant of Amon, and Kerrigan killed Narud and learned of Amon's resurrection. The campaign against the Dominion succeeded: Raynor was found alive and rescued, the Swarm invaded Korhal, and Kerrigan personally entered the palace and slew Emperor Arcturus Mengsk before the Swarm departed to fight Amon. (StarCraft II: Heart of the Swarm)

The End War and the war in the Void#

In its weakened state the Swarm still mobilized throughout the End War, winning key victories under Sarah Kerrigan, Zagara, Abathur, Alexei Stukov, and Dehaka. Kerrigan's zerg allied with the Daelaam at Ulnar, pushing into the Temple of Unification only to find the xel'naga within already dead and to fall into a trap that opened a void portal; the Swarm took heavy casualties destroying the crystals that powered it. Having rebuilt her broods, Kerrigan gathered the Dominion and the Daelaam and led the way into the Void, where the allied forces defeated Narud and freed the xel'naga Ouros. (StarCraft II: Legacy of the Void)

Ouros revealed that Kerrigan needed to ascend into a xel'naga to continue the Infinite Cycle and defeat Amon. As Zagara led the Swarm in defense of their queen, Kerrigan absorbed Ouros's essence and ascended, declaring that Zagara now led the Swarm. Kerrigan then took her broods directly against Amon, destroyed the void crystals shielding him, and delivered the killing blow, ending his reign of terror, after which the Swarm returned to the Koprulu sector. (StarCraft II: Legacy of the Void)

The Swarm under Zagara#

By 2508 the Swarm was unified under Broodmother Zagara, and a ceasefire was declared between the Swarm, the Daelaam, and the Dominion. Before departing, Kerrigan gave Zagara two gifts: the ability to choose the zerg's own fate, potentially leading them away from their warlike ways, and the location of a creature that could house xel'naga essence. Under Zagara the Swarm grew more vocal in its communication and turned toward a more peaceful stance, eventually using creatures called adostra, engineered with xel'naga essence under Abathur's direction, to regenerate the purified world of Gystt into a green jungle world. When Abathur, who despised both the adostra and Zagara's peace, attempted to spark a new war with a breed called the chitha, the Swarm joined the Dominion and Daelaam to stop him, marking the new direction Kerrigan had set for her Swarm before she left it. (StarCraft: Evolution)