Overmind: the zerg mind that betrayed Amon

The Overmind, called the Great Hungerer in the prophecy of Ulaan and the Great Betrayer by Amon, was the leader and embodied will of the Zerg Swarm. Created by Amon on Zerus to bind the zerg to a single purpose and drive them to assimilate the protoss, it was a sentient entity that gave the Swarm thought and direction while channeling its endless hunger. Though built without true free will, the Overmind came to understand its maker's plan and worked in secret to undo it, a struggle that produced the Queen of Blades and ended with the Overmind's destruction above Aiur. (StarCraft; StarCraft II: Wings of Liberty; StarCraft II: Legacy of the Void)

Creation on Zerus#

The Overmind was created by Amon and his followers on Zerus to bring order to the zerg and guide them into merging with the protoss. At first it was only a semi-sentient entity drawn from the instincts and collective sentience of the Swarm, but it quickly developed intellect and personality. Amon gave it the ability to reason while undermining its free will with an overriding directive: to perfect the Swarm by any means and to assimilate the protoss, so that purity of essence and purity of form might be joined in a being remade in Amon's image. It came to understand that the zerg would be destroyed once the protoss had been consumed, and it disagreed with its own directive, but could do little to resist it. (StarCraft; StarCraft II: Wings of Liberty; StarCraft II: Legacy of the Void)

The Overmind did not relay orders directly to every creature. As new species were folded into the Swarm, it issued its will telepathically through cerebrates, giant larva-like minds, and through overlords for direct commands. Each cerebrate led a brood of its own, and the list of every Zerg brood follows what became of them. Over centuries the zerg consumed Zerus's entire biosphere, and the Overmind, knowing it would have to leave the world to grow, lured behemoths into the system and assimilated them, granting the Swarm the means to survive and travel in space. (StarCraft; StarCraft II: Heart of the Swarm)

War with the xel'naga#

When the other xel'naga at Ulnar learned of Amon's plans and moved against him, Amon retaliated by making the Overmind aware of the xel'naga worldships in orbit above Zerus. Driven by its need to consume, the Overmind attacked, catching the xel'naga wholly off guard, and within hours the Swarm overran their defenses and laid waste to the fleet. The Overmind absorbed thousands of xel'naga, gaining their knowledge and growing far more powerful. It learned the secrets of the sacred khaydarin crystals and incorporated their energies into its own, and used what it had taken to raise the sentience of the higher zerg strains while keeping them fully under control. Even after Amon's body was destroyed, the Overmind remained bound by its directive to perfect the Swarm and seek out the protoss. (StarCraft II: Legacy of the Void; StarCraft; StarCraft II: Heart of the Swarm)

The hunt for the protoss and the coming of humanity#

The Swarm traveled in the direction of the protoss homeworld without knowing its location, destroying or assimilating countless species and laying waste to hundreds of worlds along the way. The Overmind was uneasy: the protoss possessed psionic powers it could not match, and it found no answer among the strains it devoured. The answer came when one of its deep-space probes encountered humanity, a frail race living in the shadow of the protoss yet possessed of great psionic potential. The Overmind ordered the assimilation of the terran worlds, and over sixty years its scouting broods closed on the Koprulu sector. (StarCraft)

It seeded the terran world of Chau Sara with spores as a prelude to invasion, then deliberately held its minions back to watch how the protoss responded when they arrived and scoured the planet clean. The decisive ferocity of the protoss pleased the Overmind, which pulled its forces back to study both races further. The invasion gained a powerful accelerant when Arcturus Mengsk acquired psi emitters, devices that amplified a telepath's signal and drew the zerg from great distances, and used them to turn the Swarm into a weapon against the Terran Confederacy. (StarCraft)

Kerrigan and the secret rebellion#

The zerg were drawn to Tarsonis, capital of the Confederacy, by the emitters. There Mengsk's Sons of Korhal, under the ghost Sarah Kerrigan, held the protoss back so the zerg could destroy the Confederacy, after which Mengsk abandoned Kerrigan to the Swarm. She was not killed but captured and infested. In Kerrigan the Overmind found at last a weapon to match the protoss, and beyond that a way to free itself and the zerg from Amon, whose ultimate intent to exterminate the zerg it had never forgotten. It created a cerebrate whose sole purpose was to guard the chrysalis that held her, telling it that it would live only so long as she did, and moved the chrysalis and the Swarm to Char, whose remote and convoluted terrain would shield it. (StarCraft; StarCraft II: Wings of Liberty)

Kerrigan emerged from her chrysalis as the Queen of Blades during an attack by Raynor's Raiders, and the Overmind named her the undoing of its enemies. When her mind, damaged during her ghost training, drove her to raid the science vessel Amerigo to restore her full powers, the cerebrate Zasz objected that a servant's wishes should not override the Overmind's mission; the Overmind permitted her to go, knowing she could not stray from its will. The plan to free the Swarm was now in motion even as the directive to assimilate the protoss still drove it forward. (StarCraft)

Manifestation and fall above Aiur#

The protoss Tassadar and the dark templar Zeratul conspired against the Swarm, having learned that only Dark Templar energy could permanently destroy a cerebrate. Tassadar distracted Kerrigan while Zeratul slew Zasz, an act that forged a psionic link between Zeratul and the Overmind through which each glimpsed the other's secrets. The shock of permanently losing a cerebrate threw the Overmind into mental disarray, but from Zeratul's mind it took the location of Aiur, and the Swarm turned at last toward the protoss homeworld. (StarCraft)

To assimilate the protoss the Overmind had to be made manifest on Aiur, and for that it needed a khaydarin crystal. Its forces cleared the hallowed ground of the original protoss temple, where the xel'naga had first set foot on the world, placed the crystal there, and the Overmind dove upon the planet like a bomb and implanted itself in the surface. The protoss response coalesced after a brief civil war. Praetor Fenix and Zeratul destroyed two cerebrates to weaken its defenses, and the allied assault tore away the Overmind's outer shell at heavy cost. Tassadar then set the carrier Gantrithor on a collision course and channeled the energies of the Khala and the Void through its hull into a single great ball of energy that destroyed the Overmind. In its final moments it took satisfaction that its plan to free the zerg from Amon had been set in motion, yet feared what would come should Kerrigan die. Its death is where the original StarCraft ends, and the plot of StarCraft and Brood War traces what the Swarm did next. (StarCraft; StarCraft II: Wings of Liberty)

Aftermath and legacy#

With the Overmind dead, the zerg of Aiur turned feral, and the Swarm split into two factions, one under Kerrigan and one under the cerebrate Daggoth, beginning the Brood War. Because cerebrates were not designed to live without their creator, Daggoth ordered several of his fellows to merge into a Second Overmind near the Khalis crystal, but Kerrigan coerced Zeratul into killing it before it could mature, and with the renegade cerebrates destroyed she assumed full control of the Swarm, exactly as the original Overmind had intended. For years its rotting corpse remained a site of zerg activity, fed upon and defended in equal measure. On the eve of the Second Great War, Zeratul returned to commune with its cortex and was met by the spirit of Tassadar, who revealed the Overmind's true motivations and named Kerrigan the key to saving the universe from Amon. In the End War, Amon raised his host body on the Overmind's corpse, using its dead flesh in the work, until an orbital bombardment reduced the body and most of the corpse to a charred crater. (StarCraft: Brood War; StarCraft II: Wings of Liberty; StarCraft II: Legacy of the Void)