Zerg

The zerg Swarm was a collective of biologically advanced, arthropodal aliens distinguished by their ability to evolve through the essence of other beings. Dedicated to the pursuit of genetic perfection, the zerg hunted down and assimilated advanced species across the galaxy, folding useful genetic code into their own. They took the name "the Swarm" from their capacity to spawn new strains at speed and from the relentless assaults they used to overwhelm their foes. Alongside the protoss and the terrans, they stood as one of the three great powers of the Koprulu sector, universally feared, hated, and hunted. (StarCraft (manual); StarCraft; StarCraft II: Wings of Liberty)

Creation of the Swarm#

Amon's xel'naga discovered the original zerg on the volcanic world of Zerus, where they had been the most insignificant lifeform until the fallen xel'naga turned their attention to the planet. Having abandoned their interest in physical form, Amon and his followers labored to advance the zerg toward a distinct purity of essence, making them the intended counterpart of the protoss, who had been cultivated for purity of form. The two species were meant to merge eventually into a hybrid army for Amon. At this point the species diverged: the altered Zerg Swarm on one side, and the primal zerg, who avoided the tampering and went into hiding to preserve their individuality, on the other. (StarCraft II: Heart of the Swarm; StarCraft II: Legacy of the Void)

The zerg developed the ability to assimilate other races into themselves, and Amon judged the work complete when they became conditioned to survive the harshness of space. Remembering how individual egos had ruined the protoss experiment, the xel'naga structured the collective sentience of the Swarm into a single amalgamated hive mind, creating a separate entity called the Overmind to control it and prevent any repeat of the protoss Aeon of Strife. The Overmind oversaw the Swarm's rapid evolution, created the cerebrates, and divided the Swarm into broods. The xel'naga loyal to the Infinite Cycle, sensing what was happening, opposed Amon, and in the war that followed the Swarm was unleashed upon them. Most were slain, and the Overmind assimilated their knowledge, learning of the protoss and of the directive Amon had implanted in it. From that moment the Overmind sought ways to subvert its maker's plans. (StarCraft II: Legacy of the Void; StarCraft II: Heart of the Swarm; StarCraft (manual))

The Great War and the rise of the Queen of Blades#

Having assimilated many species and evolved across the long journey, the Swarm arrived in the Koprulu sector near the Protoss Empire. The Overmind ordered the assimilation of the terrans, whose psionic potential it needed to fight the protoss. The protoss detected the zerg, recognized their xel'naga origins, and dispatched a force under Executor Tassadar to deny them a foothold. The Great War opened with the zerg invasion of the terran worlds, which neither protoss purification nor terran infighting could contain. The rebel Sons of Korhal used the invasion to topple the Terran Confederacy and raise the Terran Dominion in its place. (StarCraft; StarCraft (manual))

At New Gettysburg the zerg captured Sarah Kerrigan and withdrew to Char, where they transformed her into the Queen of Blades. The Overmind intended Kerrigan to succeed it as the Swarm's leader and so free the zerg from Amon. When the Dark Templar prelate Zeratul slew the cerebrate Zasz on Char, a brief mental link formed between Zeratul and the Overmind, through which the Overmind learned the exact location of Aiur. The Swarm invaded the protoss homeworld and devastated it, but the Overmind was slain there by Tassadar, and the protoss withdrew to Shakuras. (StarCraft; StarCraft II: Wings of Liberty)

The Brood War and the unification of the Swarm#

The Overmind's death left the Swarm divided between the cerebrate Daggoth and Kerrigan. Daggoth began creating a second Overmind, while Kerrigan sought to destroy it before it could mature and reclaim control of the entire Swarm, herself included. The civil war was complicated by the arrival of the United Earth Directorate Expeditionary Fleet, which overthrew the Dominion and captured the second Overmind, intending to use the zerg to hold the sector. The UED deployed a psi disrupter to fragment the zerg arrayed against it. Kerrigan manipulated anti-UED terrans and the protoss into destroying the disrupter and slaying the second Overmind, bringing the whole Swarm under her command at last. Betrayal dissolved her alliances of convenience, and the reformed Dominion, UED remnants, and protoss all failed to unseat her. The war closed with every faction withdrawing to rebuild and the zerg holding the worlds they had infested. (StarCraft: Brood War)

For the next four years the Swarm avoided open conflict while it expanded and evolved. The surviving cerebrates died and were replaced by broodmothers, sapient lieutenants who extended Kerrigan's control. As the first protoss-zerg hybrids became active, Zeratul learned that Kerrigan was essential to preventing the Swarm from fulfilling Amon's apocalyptic design, and he charged Commander Jim Raynor of Raynor's Raiders with ensuring her survival. (StarCraft II: Wings of Liberty; StarCraft II: Heart of the Swarm)

Kerrigan's wars and the turn against Amon#

The Second Great War began with the Swarm invading terran space in search of a xel'naga device. A joint Raiders and Dominion strike on Char used the device to restore Kerrigan to her terran form, and the Swarm fragmented again. As the Dominion hunted her, Kerrigan began reuniting the broods. The Swarm journeyed to Zerus, where it rejoined the primal zerg and Kerrigan was reborn as a primal zerg-human hybrid, a form more powerful than before and free of Amon's influence. The Swarm uncovered and destroyed a secret Dominion hybrid facility run by Doctor Emil Narud, a servant of Amon; Kerrigan killed Narud and learned of Amon's coming resurrection. She directed the Swarm against the Dominion, invaded Korhal, and slew Emperor Arcturus Mengsk in his palace before departing to fight Amon. The Swarm's leaders, from the Overmind to Izsha, each have an entry in our guide to the StarCraft characters. (StarCraft II: Wings of Liberty; StarCraft II: Heart of the Swarm)

Across the End War, the weakened Swarm fought Amon's hybrid and corrupted forces under the leadership of Kerrigan, Zagara, the evolution master Abathur, Alexei Stukov, and the primal pack leader Dehaka, winning several key victories. On Ulnar, Kerrigan rebuilt her broods and answered a benevolent voice from the Void. Joining with the Dominion and the Daelaam, she pushed into the Void, where the voice proved to be Ouros, one of the last xel'naga, who told her she had to ascend to a xel'naga to continue the Infinite Cycle and defeat Amon. While Zagara led the Swarm in defense of their queen, Kerrigan absorbed Ouros's essence and ascended, naming Zagara the new leader of the Swarm. She then struck the killing blow against Amon, and with his fall the Swarm returned to the Koprulu sector. (StarCraft II: Legacy of the Void)

Characteristics and biology#

The zerg were efficient killers, tough and tenacious, with natural armor and weaponry comparable to modern technology; their bone armor could absorb half a dozen gauss rifle rounds before breaking. One against one they were weaker than terran or protoss soldiers, but they multiplied at an alarming rate and won through numbers and mobility. They were extremely resistant to chemical agents yet vulnerable to concentrated radiation, and most strains drew nutrients from creep, a thick carpet-like substance that bound a colony's structures into a single macro-organism. Most ground strains could burrow through almost any surface and moved faster on creep than on bare ground, giving the Swarm a rapid underground transit system that made it deadly in ambush. They healed at a rate no terran field medicine could match: a gravely wounded zerg would return to full health given time, and a colony remained viable so long as a single creature or structure survived. Those few that survived a battle evolved during it, growing stronger by the hour as they studied and adapted to their enemies. (StarCraft (manual); StarCraft: Evolution; Zerg Overview (StarCraft official site); StarCraft II: Wings of Liberty; StarCraft Field Manual)

Apart from the overlord, no zerg strain bore much genetic resemblance to the organisms that spawned it, each being a custom mix of DNA assembled from the strongest cell mutations that survived to hatching. The zerg were originally selective, assimilating only strong species at the top of their food chains, but under Kerrigan they grew willing to take whatever material they encountered. The protoss remained the only species the zerg ever failed to assimilate. Their DNA could nonetheless be artificially combined to produce hybrids. The pursuit of genetic perfection sat at the core of the zerg psyche. Communication within the Swarm was largely psionic, and the zerg sensed and sought out psychic power, sometimes responding to it strongly enough to slip the control of their leader. (Broken Wide; StarCraft (manual); StarCraft II: Heart of the Swarm; StarCraft II: Wings of Liberty; StarCraft)

A new queen#

By 2508 the Swarm was unified under Broodmother Zagara, and a ceasefire was declared between the zerg, the Daelaam, and the Dominion. Before leaving, Kerrigan had given Zagara two gifts: the ability for the zerg to choose their own fate, potentially leading them away from their warlike ways, and the location of a creature that could house xel'naga essence. Under Zagara's direction the evolution master Abathur created the adostra, a breed that could passively generate life on planets as the xel'naga once had, and Zagara used them to regenerate the world of Gystt, which had been purified in the Great War. When the Daelaam came to purify the revived planet, Zagara instead extended a hand of diplomacy, offering to help the ailing factions rebuild. (StarCraft: Evolution; StarCraft II: Legacy of the Void)

Abathur despised both the adostra and Zagara's peaceful stance, which he saw as a betrayal of the Swarm's purpose. He siphoned off xel'naga essence to make the chitha, psionic zerg that could disrupt communication and command nearby zerg, and plotted to spark a new war by forcing the terrans and protoss to destroy the adostra nests. The three factions uncovered his scheme before the last nest fell, and Zagara incapacitated Abathur rather than kill him, confining him where he could do no further harm. With the One-Day War resolved, peace talks began among the three powers, with the Swarm offering aid in reconstruction in exchange for the same. The renegade broodmother Niadra later resurfaced during the Battle of Adena, ambushing a terran group to gather biomass for a purpose Kerrigan had given her years before: the destruction of the protoss. (StarCraft: Evolution; StarCraft II: Shadow Wars)