The zerg were native to Zerus, a hostile ash world near the core of the Milky Way. The first spawning pool on Zerus was the catalyst for the creation of the zerg. The pool split the genetic information ("essence") of the proto-zerg that entered it. The proto-zerg competed within; those that ate their counterparts evolved, and became the first zerg. The practice of evolution by consumption, and the principle of survival of the strongest, were fundamental to the zerg. The zerg were minature insectoids and the most insignificant lifeform on the planet. In this form they were discovered by Amon and his xel'naga, who were an ancient extra-galactic species who sought to manipulate the creations of their brethren in order to create host bodies that could end the Infinite Cycle. The Infinite Cycle merged two species, one with the purity of form and the other with the purity of essence, and would guide them to the xel'naga so they could impart their essence and live on, and Amon sought to create an army to exterminate all life to prevent the cycle from continuing. Amon and his followers previously imparted the purity of form on the protoss, and saw the zerg as ideal candidates for the purity of essence.
From their orbiting worldships, the xel'naga spurred the zerg's evolution through proto-genetic manipulation. The zerg survived and thrived; they evolved into parasites, burrowing into more resilient creatures, feeding on nutrient-rich spinal fluids, and finally gained control of their hosts. Zerg biochemistry evolved by assimilating genetic information from host species. The zerg used their new bodies to manipulate their environment. Only the most evolutionarily advanced species were made hosts and assimilated; lesser species were eradicated. The zerg ensured they remained the dominant species at all times. The zerg steered the evolution of assimilated species, mutating them to have armor-piercing spines, razor-sharp limbs, and ultra dense carapaces. The xel'naga were shocked by the rate of mutation; within a few generations the first assimilated species were unrecognizable. The diverse zerg strains became a unified species.
The zerg were united in their drive to evolve, but were still individuals. Amon's xel'naga remembered that personal pride and ego had sundered the protoss' collective consciousness, leading to the Aeon of Strife and their estrangement from the xel'naga. To avoid similar chaos, the xel'naga created the Overmind to regulate the dangers of differing egos. The foundations of the Swarm was set.
The Overmind started as a semi-sentient representation of the zerg's basic instincts and evolutionary drive, but evolved into a sentient intelligence. The Overmind created the cerebrates, giant versions of the zerg larva, to help it control the Swarm. Each cerebrate was given a specific task and control of a brood. As the Swarm expanded with new species, the cerebrates turned to queens to help manage their broods.
Some zerg hid and were strong-minded enough to escape subordination to the Overmind and, ultimately, Amon. They became the primal zerg, and continued to live as the zerg had before the formation of the Swarm. The primal zerg regarded the Swarm zerg as "corrupt".
Zerg evolution eventually approached the limits of Zerus' biodiversity. The Overmind realized the Swarm had to leave the planet and seek new life to assimilate. Extending its senses into space, it detected enormous space-faring organisms and lured them to Zerus with its psionic abilities. The organisms were assimilated into the Swarm as behemoths. and the Swarm's strains soon evolved to survive in space. This milestone was seen by the xel'naga as proof that the zerg experiment was a success.
During this time, Amon and his xel'naga were discovered by the xel'naga who were resting in Ulnar. The two factions came into conflict in the space over Zerus, with the Ulnar xel'naga seeking to end Amon's manipulations. As the Overmind extended its senses it became aware of the xel'naga worldships orbiting Zerus; and unleashed the swarm on its creators. The Overmind severed the psionic link with the xel'naga, rendering its creators blind to its actions, and launched the Swarm into orbit against the worldships. Relentless zerg attacks overwhelmed the defenders within hours. Most of the xel'naga, and their knowledge, were consumed. The Overmind processed thousands of sentient minds to grow even more powerful, and incorporated the energies of the khaydarin crystals into itself. Its creators knowledge of evolution and proto-genetic physiology was used to improve the sentience of many strains without losing control. In spite of this, some of the xel'naga escaped the culling of the zerg, and banished Amon and his followers into the Void.
Of importance to the coming interstellar journey was the xel'naga's knowledge of other species they had influenced. From this knowledge the Overmind learned of the protoss and the general location of their homeworld, Aiur, in the galactic fringe. Amon robbed the Overmind of free will by implanting an overriding directive to seek the assimilation of the protoss, thus creating the perfect species. The Overmind knew it had been subverted but could not directly act to oppose it; it realized Amon's ultimate goal would destroy the zerg.
In spite of Amon's banishment into the Void, the Overmind carried out the directive for which the Swarm was designed; perfection through the assimilation of the protoss. With Amon and the Swarm gone, Zerus was reclaimed by the primal zerg.
The zerg of the Swarm had their evolution directed to be very different from their primal forefathers. The Swarm zerg took on more skeletal physiques, bearing components essential only for combat.
The Swarm grew larger and stronger during its interstellar journey. Deep-space probes located new species, of which the strongest were assimilated to give rise to new strains. Despite these improvements, the Swarm still lacked a true answer to the psionic powers of the protoss. The answer came as they neared the Protoss Empire and probes discovered the terrans of the Koprulu sector. The terrans, a species with "primitive structures" and "poor biological adaptability", would have been below the Swarm's notice if not for their strong psionic potential. The Swarm set course for the Koprulu sector in 2439.
Zerg deep-space probes on their way to the Koprulu sector were recovered on the edge of protoss space by the Koprulu Expeditionary Force under ExecutorTassadar. The probes responded quickly and naturally to the khaydarin crystal used to scan them, a clear sign of xel'naga engineering. A hostile race engineered by the xel'naga was a clear threat. The protoss stepped up patrols for signs of the Swarm, and sent Tassadar's force to the Koprulu sector to counter the invaders. Infestation was already in progress when they arrived.
The Swarm immediately infested some Fringe Worlds upon arriving in the Sector. Penetrating deeper, they arrived in the Sara system. The infestation of Chau Sara was subtlely spearheaded by hive spores, followed by the bulk of the zerg force to complete the process. The Terran Confederacy sought to keep the zerg a secret from its own citizens, while using the zerg as a tool to secure its power. Confederate manipulation ultimately failed. Ironically, the anti-Confederate group the Sons of Korhal would succeed in using the zerg to destroy the Confederacy.
The Swarm's invasion inexorably made its way to Tarsonis, the capital of the Confederacy. The uses of the psi-emitters by the Sons of Korhal at Mar Sara, Antiga Prime, and finally Tarsonis influenced the path of the invasion. The Koprulu Expeditionary Force followed close behind, purifying infested worlds as the terran abandoned them. The Overmind ordered the Swarm not to resist the protoss, so that it could observe the protoss in action.
At Tarsonis, the Sons of Korhal fought the protoss to allow the Swarm to complete the destruction of the Confederacy. Arcturus Mengsk unwittingly aided the Swarm by abandoning Lieutenant Sarah Kerrigan, allowing the Swarm to capture her and achieve its objective. The Overmind hoped that as a human-zerg hybrid, Kerrigan would free the Swarm from Amon's malignant influence. The Swarm placed Kerrigan in a chrysalis and withdrew the bulk of its forces to Char, now the Swarm's primary hive world in the sector. In its wake the Terran Dominion rose to replace the Confederacy. There was also a growing rift between Executor Tassadar and the Conclave over the former's unwillingness to deal decisively with the zerg in order to spare terrans; the Conclave would eventually consider the insubordinate Tassadar a more immediate threat than the zerg, hampering the Protoss Empire's response to the zerg invasion of Aiur.
Inside the chrysalis, a maturating Kerrigan's psionic emanations drew terrans and protoss to Char. Kerrigan emerged from the chrysalis as the Queen of Blades and immediately joined the fighting. Kerrigan retained a strength of will and independence uncommon within the Swarm; this was to the Overmind's design. With expeditions from the Terran Dominion and Raynor's Raiders repelled, Kerrigan boarded a terran science vessel and obtained Dominion Ghost Program files to break her psionic conditioning. With her powers unfettered she detected Tassadar and the remnants of the Koprulu Expeditionary Force on Char, but not his Dark Templar allies led by Dark PrelateZeratul. While Tassadar distracted her, Zeratul struck and permanently slew Zasz; the Garm Brood ran amok without its leader and was purged. The death of Zasz left the Overmind temporarily unable to communicate.
The protoss were undone by their victory. A brief psionic link formed between Zeratul and the Overmind at the moment of Zasz's death, and each read the other's mind. The Overmind learned the secret location of Aiur.
Kerrigan remained on Char to continue her punitive campaign against the protoss even as the Swarm departed to invade Aiur. The protoss suffered heavy casualties but Tassadar and Zeratul survived and proved frustratingly elusive. The protoss were joined by Jim Raynor and survivors of the Raiders who could not escape Char. This unlikely alliance exploited Kerrigan's impatience to kill another cerebrate. Eventually, Tassadar and Raynor were trapped on Char Aleph and Zeratul was trapped in an abandoned terran installation on the surface. They would all be rescued by Executor Artanis.
In the initial stage of the invasion, the Overmind made landfall on the same spot the xel'naga had first landed on Aiur. The Conclave appointed Artanis as the new executor; Artanis achieved tactical victories. From Char, Tassadar advised the protoss to cripple the invaders by killing cerebrates, but this proved ineffective as the protoss of Aiur did not wield the powers of the Void. Even as the invasion worsened, the Conclave dispatched Artanis and a fleet to Char to arrest Tassadar. To the Conclave's chagrin, Artanis returned allied with Tassadar, Zeratul, and Raynor.
The brief protoss civil war finally united the protoss camp; the Conclave tactfully joined a united front against the zerg. The Nerazim killed cerebrates defending the Overmind, opening the way for a strike on the Overmind. Tassadar drew upon the Void and sacrificed himself to destroy the Overmind.
It was a hollow victory. The Swarm was thrown into disarray; the zerg on Aiur rampaged and caused even more destruction. The protoss were forced to abandon the planet for Shakuras, the homeworld of the Nerazim.
The death of the Overmind plunged the Swarm into civil war.Daggoth led other cerebrates into merging together to form a new Overmind on Char; in the meantime they controlled most of the broods. Kerrigan and most of the remaining broods opposed them. Kerrigan sought to destroy the new Overmind, before it could mature and gain control over the entire Swarm and her, and take control of the Swarm.
Kerrigan acquired, and manipulated, the needed allies on Shakuras. Before approaching the protoss, she psionically dominated MatriarchRaszagal of the Nerazim. Kerrigan was aided by the immediate threat Daggoth's Swarm posed to Shakuras. Some of Daggoth's zerg followed the protoss evacuation of Aiur to Shakuras; the protoss killed two cerebrates nesting near the xel'naga temple. Kerrigan's offer to aid the protoss to activate the temple and secure Shakuras in return for aid against the new Overmind was accepted with Raszagal's support. Recovering the Khalis took Kerrigan and the protoss to Char and into combat against Daggoth's Swarm.
Aldaris discovered Kerrigan's influence over Raszagal and led a Khalai revolt on Shakuras. Raszagal ordered Zeratul and Artanis to put down the revolt and kill Aldaris. However, instead the prelate and executor offered reconciliation in exchange for Aldaris' renewed cooperation. The judicator refused and was killed by Kerrigan before he could reveal her deception. The protoss were outraged by Kerrigan's interference; the alliance was broken but she left the planet having ensured the deaths of two enemy cerebrates. The protoss subsequently activated the Shakuras temple and scoured the zerg from the planet.
The zerg civil war was complicated by the arrival of the United Earth DirectorateExpeditionary Fleet with orders to take control of the Overmind and take control of the Koprulu sector. Even as the Terran Dominion fell to the UED, Kerrigan was preparing to remove the new invaders. She used Jim Raynor's conflicted feelings for her to gain the cooperation of Raynor's Raiders; in turn, Raynor secured aid from the protoss of Shakuras for her. The Raiders and Fenix helped Emperor Arcturus Mengsk evade capture by the UED Like with her prior protoss allies, she used the threat of a greater enemy to gain cooperation.
For a time, Kerrigan was aided by an agent in the UED. Samir Duran was an entity secretly allied with Amon, but assumed constructed identities to enter the confidence of Kerrigan and UED. Duran joined the UED disguised as a terran anti-Dominion rebel, actually working for Kerrigan to sabotage the UED. Duran played a key role in Mengsk's escape. However, he was exposed in a failed attempt to destroy the original psi disrupter on Braxis; before fleeing the UED he mortally wounding Vice Admiral Alexei Stukov. After that, Duran was known by the infested terran layer of his disguise.
The intact psi disrupter proved vital to the UED. It disrupted zerg control throughout the Sector, allowing the UED to attack Char and capture the Overmind. This gave the UED control over several broods. Their tenuous hold over the Overmind limited the distance that broods could be controlled through remote means alone.
The psi disruptor gave the UED a significant advantage. It granted it control over broods, disrupted Kerrigan's control over her broods, and prevented her from controlling broods not yet claimed by either side. Kerrigan had planned for this when she had Mengsk rescued. Mengsk agreed to loan psi-emitters in exchange for the return of Korhal to the Dominion. . Kerrigan used the emitters to gain control of feral zerg on Braxis, which she used to destroy the psi disrupter. After a build-up the allies moved on Korhal. The defenses, reinforced by UED zerg, were broken. Korhal was restored to the Dominion, and the UED lost their primary staging point in the sector. With Char the only remaining UED stronghold, Kerrigan no longer needed her allies. Before leaving Korhal, she struck heavy blows against the Dominion and protoss, killing General Edmund Duke and Fenix.
The UED used zerg to attack Kerrigan on Tarsonis, but the attack failed due to brittle control.
Kerrigan coerced Zeratul and the Nerazim into killing the second Overmind on Char by taking Raszagal hostage. With the Overmind and its supporting cerebrates dead, Kerrigan gained control of the zerg in the Koprulu sector. Zeratul discovered Raszagal was enthralled to Kerrigan; the zerg blocked the protoss' escape with the matriarch, and Zeratul slew Raszagal rather than allow her continued enslavement. Zeratul's force was subsequently scattered. Afterwards, Duran abandoned the Swarm and his infected terran guise to return to his true work, the creation of hybrid. Kerrigan's assimilation into the Swarm had been a boon to this effort.
The Dominion, protoss, and UED struck at Char with unexpected alacrity before the zerg could consolidate. The zerg held and the all assailants were forced to retreat. The Swarm were secure, and Kerrigan emerged as the Sector's dominant power. After the destruction of the fleeing UED fleet by the Swarm, the belligerents were finally exhausted and an uneasy peace fell over the sector. The zerg retained worlds they had infested.
Intermittent fighting continued between the end of the Brood War and the start of the Second Great War even as the powers withdrew to recover. The Swarm refrained from overt hostilities against the terrans and protoss, and engaged only in occassional skirmishes. The Swarm destroyed all expeditions to its worlds.UNN and other terran news services that covered general threats did not report on the zerg during this time, and observers could only speculate on the Swarm's restraint.
The Swarm sought out new worlds and species to infest and used spies to collect xel'nagaartifacts. In 2502, the Swarm were estimated to have infested over a hundred worlds. In 2503, the Swarm attempted to capture archeologist Jake Ramsey while he carried the consciousness of the protoss preserverZamara. Ramsey and Zamara also interested the other powers and the resulting clash allowed them to escape the Swarm.
New strains were created. The baneling was bred from the attack on the terran colony on Sorona. In accordance to Kerrigan's vision for the Swarm, the cerebrates were destroyed and replaced with broodmothers. The broodmothers were made to evolve their broods  and respect only strengh; these qualities exacerbated the fragmentation of the Swarm during the Second Great War.
The New Swarm was created by cerebrate Kaloth as an experiment in human-zerg hybrid leaders. Kaloth resurrected and infested Alexei Stukov, who led the New Swarm as a conglomerate of zerg and renegade terrans on Braxis. The New Swarm did not last long. It dissolved when Stukov was temporarily deinfested by a protoss nanite serum delivered by Jim Raynor. Stukov was given to the Moebius Foundation so they could study the nanites. When the nanites failed and his infestation returned he was experimented upon. He was imprisoned at the Terran Dominion's Skygeirr Station, where Emil Narud, a servant of Amon working to resurrect his master, created hybrid.
The zerg on Aiur remained part of the Swarm but they escaped strong control. From the chaos of the first Overmind's death, these zerg had regained some intelligence, but were still less vicious and focused and they did not reproduce. This hampered Swarm operations on Aiur.
At the end of the Brood War, Kerrigan already had forebodings for the future. Narud would later claim Amon "told" her these portants of doom. In the following years, Kerrigan learned something of Duran's activities. What she learned of Amon's coming catalysm caused her to lose all hope for the future. Nonetheless, she resolved to fight it and sought out a xel'naga prophecy on Ulaan for further information. As Kerrigan expected, Zeratul arrived searching for the same prophecy. The Nerazim prelate found the prophecy and took it away before Kerrigan could see it. Zeratul learned through the prophecy that Kerrigan was needed to stop Amon; Zeratul would assist her in the coming conflict.
In addition to the prophecy, Kerrigan wished to acquire components for a xel'naga device which were scattered across the sector. In 2503 the Swarm was nearly recovered from the Brood War. The next time the Swarm invaded the Sector in strength, one of its tasks would be to search for and retrieve the components. On the eve of the Second Great War, the Swarm had made good past damages; Char alone was estimated to have over ten billion zerg in 150 primary and 1029 tertiary hive clusters.
Kerrigan had many reasons to unleash the Swarm on the Sector and starting the war. For the Swarm, there was the search for the xel'naga device and the drive to evolve. For herself, there was the desire for action and revenge against Emperor Arcturus Mengsk of the Terran Dominion The Swarm offensive achieved strategic surprise.
The zerg advanced on all fronts. The Dominion Armed Forces suffered heavy casualties to slow the advance. A major contributing factor to the Dominion survival was that the Swarm was not immediately concerned with systematically destroying it.
While the Swarm conquered worlds, it had no success with the xel'naga device. In competition with the Swarm, Raynor's Raiders recovered all the components and delivered them to Crown Prince Valerian Mengsk of the Terran Dominion. With the components in terran hands, the Swarm slowed its offensive in terran space.
Valerian planned to use the xel'naga device to deinfest Kerrigan. A joint Terran Dominion and Raynor's Raiders force attacked Char to deliver the device in range of Kerrigan.
Though most if the Swarm was off-world, the remainder was sufficient to win through attrition given time. Kerrigan recalled the closest broods invading the Dominion as reinforcement, although they would ultimately not arrive in time. The invasion worked to Kerrigan's advantage; the terrans had literally delivered the complete xel'naga device to her.
The terrans compensated for their lack of time and numbers with operational surprise and audacity. The device deinfested and removed the last vestiges of Amon's influence from Kerrigan. She was saved from would-be-assassin Tychus Findlay, working for Mengsk, by Raynor. Raynor was motivated by his old feelings for her and by Zeratul; after deciphering the prophecy on Ulaan, Zeratul had implored Raynor to ensure Kerrigan's survival.
The psionic energy released by Kerrigan during deinfestation may have been collected by hybrid and used to complete the resurrection of Amon.
The removal of the Queen of Blades marked the start of another period of disunity within the Swarm. Broods scattered over the Sector became independent under their respective broodmothers. The fragmentation aided the Terran Dominion's zerg-extermination campaign on Char. Zagara, the broodmother, on Char, fought an unsuccessful campaign against them.
A deinfested Kerrigan was taken to Research Station EB-103 in the Umojan Protectorate where she rekindled her personal relationship with Raynor. A Dominion attack forced them to flee and they were separated. Kerrigan escaped but Raynor was captured and reportedly executed. This enflamed her desire for revenge against Mengsk. To pursue this she would wield the Swarm.
Kerrigan journeyed to her leviathan to resume control of the Swarm. The Swarm's fragmentation made an immediate assault on Korhal impossible. Kerrigan was reunited with broodmother Zagara during the reconquest of Char from the Dominion. Kerrigan had Abathur enhance Zagara's intellect, ultimately making the broodmother an adaquete replacement leader for the Swarm. This violated a long-standing imperative that prevented competition over the Swarm's leadership; Kerrigan found this acceptable.
Kerrigan's transformation back into a human-zerg hybrid was pivotal. Driven by the prophecy from Ulaan, Zeratul guided her to Zerus to be transformed using the primal zerg-human hybrid; Kerrigan was motivated only by revenge against Mengsk. Kerrigan emerged from the first spawning pool more powerful than her old hybrid form and free from Amon's influence. Furthermore, whereas before she could merely "hear" and "control" the Swarm, now she could "feel" and "be" it. Her power increased by defeating and absorbing the essences of the other primal pack leaders. The Swarm returned to the Koprulu sector with Dehaka and other primals.
The broodmothers gradually returned to the Swarm as Kerrigan's psionic powers and list of victories grew; the rejoining broods were sent to cripple the Dominion's war effort.
Kerrigan learned Raynor was alive and being held hostage by the Dominion; he would be executed if the Swarm moved on Korhal. With the aid of Raynor's Raiders, Kerrigan found and rescued Raynor from the prison ship Moros.
The Swarm found new purpose at Skygeirr Station, home of the Dominion's hybrid production program led by Doctor Emil Narud. The Swarm found the secret installation with the aid of infested Stukov and destroyed it. Kerrigan killed Narud and learned of Amon's resurrection. Kerrigan recognized the extreme danger posed by Amon; the Swarm would seek out and fight Amon, although she regarded this as a hopeless battle.
The Swarm converged on Korhal. Valerian agreed to Kerrigan's bid to kill Mengsk. In turn, she endored Valerian as his father's successor and agreed to avoid unnecessary civilian casualties. Dominion fleets deployed outside the system responded quickly and were engaged by the Swarm's contravallation. The Swarm braved ferocious anti-orbital fire to establish a planethold outside of Augustgrad. The city was protected by the Psi Destroyer, which killed zerg linked to the hivemind; the primal zerg, hitherto unknown to the Dominion and unlinked to the hivemind, were immune to the Destroyer and spearheaded the assault that destroyed it. The Swarm was joined by Raynor's Raiders as it surged into the city and broke into the Korhal Palace. Kerrigan confronted Mengsk inside. Raynor's intervention prevented the emperor from killing her using the xel'naga device, and allowed Kerrigan to kill Mengsk.
The Swarm withdrew from Korhal to wage war against Amon.
Zerg under Kerrigan's command assaulted a Moebius Foundation base whose personnel had come under the thrall of hybrids. It was successfully destroyed.
Kerrigan then sent her broods to find the xel'naga at Ulnar. However, she found that the hybrid were already there, and she began engaging in a battle against them that lasted days.
On Aiur, the Daelaam launched an assault on the feral zerg on Aiur. However, the zerg had already come under the control of Amon's hybrid, and they began to use organized tactics against the Daelaam. When Amon corrupted the Khala, the Amon Brood fought alongside the corrupted protoss and the hybrid in order to push Artanis and his few loyal protoss off the planet. The corpse of the dead Overmind was then used by Amon in order to begin construction of a hybrid host body.
The warp gate linking Shakuras to Aiur was then reactivated, and Amon's zerg flooded through, swarming the city of Talematros. Artanis and the Daelaam arrived in time to evacuate the city and clear the launch bays of zerg infestation, but the zerg presence on the planet had already hit critical levels.MatriarchVorazun refused to allow her planet fall to the zerg, and ordered the xel'naga temple's phase matrix be overloaded, destroying the planet. Over a billion zerg and hybrid were destroyed in the process.
Artanis arrived at Ulnar using the Keystone to guide him, and met with Kerrigan. The two attempted to release the xel'naga, but had found that they were already dead. Amon then released a void portal in Ulnar and began flooding the area with void energy. Kerrigan used her zerg to take the brunt of the void energy while Artanis closed the void portals. The strategy was successful, but Kerrigan's broods were devastated.
On Endion, Amon sent his broods to infest the moon. The Daelaam arrived in order to reactivate the Purifiers on the station orbiting the moon, and fought through the hives on the moon in order to deactivate the stasis locks shielding the warship Cybros. The plan was successful, but Amon's zerg swarmed the platform with the help of hybrid. The Daelaam activated the Purifiers, who purged the platform, then fired a purification beam on Endion, destroying all zerg on the planet.
When the Daelaam returned to Aiur, Amon used his broods as his first line of defense. The zerg defended the first khaydarin crystal powering the psionic matrix in Antioch, and hives defended the third crystal in the xel'naga caverns beneath Aiur, but were overcome by the protoss. Amon's brood then defended its master's host body when the Daelaam assaulted it, but the void shards shielding him were destroyed. While Amon's host body was awakened, it was quickly destroyed by an orbital bombardment. The zerg then swarmed the Daelaam as they set up the Keystone, and were supported by the corrupted Golden Armada. This was not enough to destroy the Keystone in time, and the zerg on Aiur were severed from Amon's control.
On Ulnar, Kerrigan called to Raynor and Artanis, telling them of the benevolent voice in the Void calling to her, and that Amon still existed in the Void. The three agreed to destroy Amon, and used Ulnar's void portal to gain access into the Void. Kerrigan and Stukov lead the zerg to free what they thought was Tassadar's spirit from Narud, and broke through his lines of shadows of the Void to get to him. Stukov slew him, getting revenge for the years of torture inflicted on him. Tassadar's spirit revealed itself to be the xel'naga Ouros, who needed to ascend Kerrigan into a xel'naga in order to complete the Infinite Cycle and give the universe a chance at destroying Amon.
Kerrigan began channeling Ouros's essence, but Amon began sending forces to stop the process. Zagara lead the zerg to defend the eastern approach, and was aided by Jim Raynor and Artanis. The defense was successful, and Kerrigan ascended into a xel'naga. She put Zagara in charge of the zerg swarm, and told her to remember the lessons she had taught her. Kerrigan then took the swarm for the final confrontation against Amon.
Kerrigan lead the swarm to destroy the void crystals defending Amon, and was supported by Jim Raynor and Artanis. With the combined force, the void crystals were destroyed, and Kerrigan delivered the killing blow to Amon.
Upon returning to the Koprulu sector, Zagara took complete control over the Zerg Swarm. By 2508, she had seized control of Char and the worlds surrounding it.
Years later, feral zerg attacks began to hit Antiga Prime and Bountiful, drawn by psi-emitters placed by a separatist militia known Defenders of Man. While the Terran Dominion were slow to respond, the Defenders of Man successfully evacuated these colonies, claiming the Dominion was too slow and weak in the face of the alien threat. Meanwhile, the Dominion investigated the incidents, discovering the Defender's goals, but not before they released the zerg on Borea and Tyrador IX, leading to massive loss of life. The Defenders and Dominion were able to repel the feral zerg.
↑Zasz: "Though you be the favored servant of the Overmind, you would do well to remember that you are just a servant. You know of our grand mission, Kerrigan. Would you put your personal whims before the will of the Overmind?" Kerrigan: "Do not cross me, Zasz. I will do as I see fit, and not you or any other Cerebrate shall stand in my way." Overmind: "Let her go, Zasz. The greatness of her spirit has been left to her; that the Swarms might benefit from her fierce example. Fear not her designs, for she is bound to me as intimately as any Cerebrate. Truly, no Zerg can stray from my will, for all that you are lies wholly within me. Kerrigan is free to do as she desires." StarCraft. Vivendi Games. Level/area: The Amerigo (in English). 1998.
↑Overmind: "Yet shall their overweening pride be their downfall. For when the assassin Zeratul murdered Zasz, his mind touched with mine, and all his secrets were made known to me. I have taken from his mind the secret location of Aiur, the Protoss Homeworld." StarCraft. Vivendi Games. Level/area: Eye for an Eye (in English). 1998.
↑Fenix: "Executor, I bring news most dire. The Cerebrate that we thought we had killed has arisen again. The creature's battered form was reincarnated, despite the considerable damage we inflicted upon it. Even now, the Cerebrate drives its Brood in preparation for their next offensive." StarCraft. Vivendi Games. Level/area: Higher Ground (in English). 1998.
↑Aldaris: "Executor. Tassadar. This comes too late to you. But the Conclave has witnessed your defeat of the Cerebrate. They know now that they cannot deny the necessity or the valiancy of your actions. We sought to punish you, while it was we who were in error. You represent what is greatest in us all, and all our hopes go with you. EN TARO ADUN, brave Sons of Aiur!" StarCraft. Vivendi Games. Level/area: Eye of the Storm (in English). 1998.
↑Kerrigan: "Apparently, many of the renegade Cerebrates, commanded by Daggoth, have merged into a new Overmind. Fortunately, the creature is still in its infant stages. It can't control the Swarm yet, but Daggoth and the others still have control over most of the Broods." StarCraft: Brood War. Vivendi Games. Level/area: The Quest for Uraj (in English). 1998.
↑Kerrigan: "Look, I don't need to tell you all what might happen if that thing reaches maturity. I can guarantee you that should it awaken, it'll take full control of me just like it did before. I don't want that to happen, and I'm pretty sure you don't want it to happen either." StarCraft: Brood War. Vivendi Games. Level/area: The Quest for Uraj (in English). 1998.
↑Raszagal: "Congratulations, Executor. Your success has brought us the promise of hope against the Zerg. However, we face a new threat within our own ranks. In your absence, Judicator Aldaris and an entire legion of Khalai survivors from Aiur have begun an open revolt against us." Zeratul: "By the gods, this is ill news indeed! Why would Aldaris betray us so?" Raszagal: "He and his ilk believe that it was wrong to have abandoned Aiur and consorted with our people. Their prejudices have driven them to perpetuate the Conclave's sins against us! Even now, Aldaris and his loyalist templar forces are preparing to attack our Citadel." Artanis: "I can scarcely believe this. As if the Zerg were not enough! Matriarch, are you certain of this?" Raszagal: "All too certain, young templar. Executor, as Matriarch of the Dark Templar and custodian of this world, I hereby order you to terminate Judicator Aldaris, and quell this untimely uprising without delay! There will be no dissent among us while the Zerg are poised to strike!" StarCraft: Brood War. Vivendi Games. Level/area: The Insurgent (in English). 1998.
↑Aldaris: "You can no longer afford to be so naive, Artanis. While you were securing the crystals, I discovered that your Matriarch has been harboring a dark secret! She has been manipulated by de-" Kerrigan: "We have no time for this!" Zeratul: "Kerrigan... What have you done?" Kerrigan: "I just cleaned up your mess, Protoss. Don't be so squeamish." Zeratul: "Wretched creature! This was a Protoss matter; you had no right to interfere! Begone from this world! You are no longer welcome among us!" Kerrigan: "Fine. I've done what I came here to do. I've insured the destruction of the renegade Cerebrates, and I used you to do it. Have fun, mighty Protoss... We'll be seeing each other again, real soon..." StarCraft: Brood War. Vivendi Games. Level/area: The Insurgent (in English). 1998.
↑Samir Duran: "Captain, I am Lieutenant Samir Duran of the Confederate Resistance Forces. I've been monitoring your attack against the Dominion, and I'd like to offer you my services and skills in return for amnesty." Alexei Stukov: "Intriguing. Lieutenant, you have absolutely no idea as to who we are or what we have come here to do. Why do you wish to side with us?" Duran: "Because my men and I have sworn to fight against the Dominion and its Emperor. Seeing as how your forces have been laying into this Dominion base, I figured we were on the same side." Stukov: "I see. How exactly do you propose to be of service to us, Lieutenant?" Duran: "Well, I possess intimate knowledge of the surrounding area. I can show you an alternate route that leads to the rear of the main Dominion base." Stukov: "Very well, Lieutenant. Consider yourself and your men the first colonial conscripts of the United Earth Directorate. Captain, see that the Lieutenant is given our full cooperation. We shall see if he's worth the effort." StarCraft: Brood War. Vivendi Games. Level/area: First Strike (in English). 1998.
↑Duran: "Vice Admiral Stukov, I am here under orders to terminate your command." Stukov: "Lieutenant Duran. I'm not surprised. We both know exactly what it is that you're here to terminate. Get on with it." Duran: "Say goodnight, Stukov." Stukov: "To hell with y- !" Gerard DuGalle: "Lieutenant Duran, report your situation immediately!" Stukov: "Gerard... old friend. You do indeed have a traitor in your midst... but it's not me. Duran. He has been playing us both from the start... He convinced you to destroy the Psi Disrupter... even though it was our best chance at defeating the Zerg. And then, on Aiur, ...he allowed the Zerg to overrun us even as we had the fugitives in our grasp. I came here... to activate the one hope we have of defeating them... And you killed me for it. Heh, heh... Duran is your enemy Gerard. I suspect... that he may even be infested as well... Use the Disrupter, Gerard... Finish our operation... Let my death have at least some meaning." DuGalle: "Alexei! No! What have I done? What have I done? Computer, where the hell is Lieutenant Duran?" Adjutant: "The Lieutenant no longer registers on my sensors, Admiral. He appears to have vanished." DuGalle: "No." StarCraft: Brood War. Vivendi Games. Level/area: Patriot's Blood (in English). 1998.
↑Duran: "My Queen, we have located a small Terran facility towards the rear of the Renegades' landing zone. There appears to be a number of UED scientists working within the compound, but we are unable to determine the purpose of their presence..." Kerrigan: "I know what they're up to. I suspected that the UED's control of the Overmind was tenuous. Tarsonis is too remote for them to maintain direct control over the Swarms, so they've sent these 'scientists' to coordinate their attack." Duran: "Cerebrate, focus your attacks against the Terran facility. All of the UED scientists must be killed. Only then will we be able to finish off these Renegade Zerg." StarCraft: Brood War. Vivendi Games. Level/area: Fury of the Swarm (in English). 1998.
↑Zeratul: "Kerrigan, this is Zeratul. I demand to know why you've taken our Matriarch." Kerrigan: "Actually, Zeratul, she's not the one I'm truly interested in. I stole her to get to you. You see, I need you and your brethren to kill the Overmind for me. The only way I had of assuring your cooperation was to take away that which you value most. However, I give you my word that once you've killed the Overmind, I'll allow her to return to you." Zeratul: "As if your word held any value..." Raszagal: "Zeratul, my faithful servant. You must aid Kerrigan in this endeavor. The Overmind is our common enemy. It must be destroyed to insure that our people will survive!" Zeratul: "You ask me to aid this vile creature?" Raszagal: "I do not ask this for myself. Nor do I ask it on Kerrigan's behalf. I ask you to do this for our people, Zeratul. Obey me as you always have... Trust in my judgement." Zeratul: "Very well, Matriarch. The Overmind will die this day." StarCraft: Brood War. Vivendi Games. Level/area: To Slay the Beast (in English). 1998.
↑Zeratul: "It's done, Kerrigan. The Overmind is dead as you wished. Now I demand that you release the Matriarch at once!" Kerrigan: "Of course. Raszagal, do you wish to return to your tribe?" Raszagal: "No, my Queen. I wish only to serve you and remain at your side." Zeratul: "What treachery is this, Kerrigan? This pathetic creature cannot possibly be Raszagal!" Kerrigan: "Ha ha ha. I promised that I'd allow her to return to you, Zeratul. But it looks to me like she doesn't want to go." Zeratul: "You have corrupted her! Somehow you have poisoned her thoughts. Restore her to her rightful self, or you will pay dearly for this offense, Kerrigan!" Kerrigan: "All right, Zeratul, you've got me. I made your Matriarch my slave long before I joined you on Shakuras. She made the mistake of underestimating my power just like everyone else did." StarCraft: Brood War. Vivendi Games. Level/area: To Slay the Beast (in English). 1998.
↑Zeratul: "Damn you, Kerrigan, for what I must do!" Raszagal: "Thank you, Zeratul... You have freed me from her vile control at last. You have always served me with honor... Thus I must ask you... to watch over my tribe... Into your hands I give the future." Kerrigan: "I can hardly believe this! You've killed your own Matriarch!" Zeratul: "Better that I killed her, than let her live as your slave, Kerrigan." StarCraft: Brood War. Vivendi Games. Level/area: The Reckoning (in English). 1998.
↑And alone, floating on a dark platform above the burnt-out planet of Char, Sarah Kerrigan, the Queen of Blades, sat and lorded over the ravenous Swarms. Unable to shake the feeling that a great threat loomed just over the horizon, Kerrigan could only stare off into the vastness of space where she beheld a great void. Or perhaps a reflection of a hollow victory and of the trials yet to come... StarCraft: Brood War. Vivendi Games. Level/area: Epilogue (in English). 1998.