Hybrid

The hybrid were an engineered fusion of the protoss and the zerg, described as false xel'naga and built to serve as the ultimate weapons of the fallen xel'naga Amon. Their creation was a perversion of the Infinite Cycle: rather than allowing a species pure of form and one pure of essence to come together naturally, Amon and his followers forced the protoss and zerg into a single creature meant to end the cycle entirely and remake creation in his image. Knowledge of the hybrid spread among terrans, protoss, and zerg, and most who learned of them understood the threat they posed to all life. (StarCraft: Brood War; StarCraft II: Wings of Liberty; StarCraft II: Legacy of the Void; StarCraft: The Dark Templar Saga: Twilight)

A weapon against the cycle#

The xel'naga reproduced by seeding the universe with life as part of their Infinite Cycle. In time two species would emerge, one pure of form and one pure of essence, and through peaceful means they would come together, allowing their xel'naga progenitors to pass on their essence and give rise to the next generation of xel'naga. The xel'naga watched over the younger races but never interfered in their development. (StarCraft II: Legacy of the Void; StarCraft: The Dark Templar Saga: Twilight)

Amon viewed this cycle as corrupt and as the source of all suffering. He gathered a group of like-minded followers and set out to find two races he could uplift and groom into a perfect life form that would end the cycle. He uplifted the protoss of Aiur to be pure of form, then traveled to Zerus and uplifted the zerg as pure of essence, creating the Overmind to enforce that purity. The hybrid were to be the product of merging the two, but because they were forced rather than allowed to arise naturally, their creation would not lead to the rebirth of the true xel'naga. When the other xel'naga discovered his experiments and moved to stop him, Amon unleashed the Overmind and the Swarm against their worldships over Zerus, wiping out most of his own kind and throwing the cycle into turmoil. The Swarm then sought to complete the work by absorbing the protoss, but the Khala and the Void shielded them from infestation, leaving the hybrid as the only path to the fusion Amon desired. (StarCraft; StarCraft II: Legacy of the Void)

Duran's experiments#

To fulfill Amon's design, Samir Duran worked to produce a perfected protoss-zerg hybrid as a stepping stone toward a far more powerful host body capable of sustaining his master. He established development bases on multiple worlds and created numerous specimens, and the work was accelerated by Sarah Kerrigan's assimilation into the zerg. Duran claimed the hybrid was the completion of a cycle whose role in the cosmic order had been preordained when the stars were young. (StarCraft: Brood War; StarCraft II: Legacy of the Void)

One such base, on a dark moon, was discovered by chance by Dark Prelate Zeratul as he returned from Char, where he had slain the second Overmind and Matriarch Raszagal. Seeking to rendezvous with Praetor Artanis, Zeratul mistook the protoss energy signatures from the moon for stragglers, but found instead a hybrid development base staffed by terran mercenaries using protoss technology, with protoss, zerg, and infested terran specimens held in stasis. Horrified by the hybrid specimen he found there, Zeratul destroyed it before departing. Duran contacted him to reveal that the experiments were sponsored by a greater power and that specimens were hidden on many worlds. Zeratul kept the discovery secret and set out on a solitary fact-finding journey in 2503. Separately, the rogue dark templar Ulrezaj bred strange creatures beneath Aiur after its fall, which the preserver Zamara, lodged in the mind of the archaeologist Jake Ramsey, suggested might be a form of hybrid. (StarCraft: Brood War; StarCraft II: Heaven's Devils; StarCraft: The Dark Templar Saga: Shadow Hunters)

The Second Great War#

The hybrid were released on the eve of the Second Great War. The hybrid destroyer Maar seized the protoss archive world of Zhakul, leeching the energies of its preservers and subverting its Zhakul Guardians before Zeratul stopped it. By this time hybrid experiments were also under way at a secret Terran Dominion facility orbiting Castanar, using gene-splicing technology far more advanced than anything the terrans possessed. When Raynor's Raiders attacked the Castanar facility, they found hybrid being cloned and inadvertently released a powerful hybrid reaver that rampaged against protoss, zerg, and terran alike. (StarCraft II: Wings of Liberty)

Prior to 2504, Doctor Emil Narud of the Moebius Foundation created at least three hybrid aboard Space Station Prometheus, concealing from his benefactor Valerian Mengsk how far the work had gone. Narud later turned the hybrid against Valerian and Jim Raynor, while Arcturus Mengsk, who also knew of them, claimed a specific psionic signal could pacify the creatures. A recovering Sarah Kerrigan unleashed her psionic power and killed two of the hybrid, and the last was destroyed as Narud escaped with the xel'naga artifact. Kerrigan and her Swarm later encountered hybrid dominators aboard Skygeirr Station, overcoming them and the Tal'darim who fought alongside Narud. Kerrigan slew Narud in single combat, but as he died he revealed that Amon had already been revived. (StarCraft II: Flashpoint; StarCraft II: Heart of the Swarm)

The End War and Armageddon#

After the Second Great War the hybrid began to awaken on their own, seizing control of the Moebius Corps and Moebius Foundation personnel who had created them and turning them into thralls. Zeratul and Sarah Kerrigan fought hybrid-controlled forces at several sites, and Zeratul faced them again at the Temple of Erris on Atrias, where Amon himself emerged from the Void. Once the war was joined, the hybrid served as Amon's most fearsome troops. They coordinated the Amon Brood zerg during the assault on Aiur, helped besiege the xel'naga temple of Shakuras, and channeled Void energy into the Keystone during the siege of Korhal. The Daelaam and their allies hunted the breeding facilities to their source, with Phase-smith Karax leading the assault on Revanscar, where the majority of hybrid had been created, and the Spear of Adun firing on the facility to end the operation. (StarCraft II: Legacy of the Void; Sector Six)

The full horror the hybrid represented was foretold in the Overmind's apocalyptic vision, which Zeratul uncovered through Tassadar's spirit while pursuing a prophecy from Ulaan. In that future the zerg were enslaved by Amon and the hybrid after Kerrigan's death, the terrans were annihilated, and the combined hybrid-zerg host destroyed the protoss before turning on and eliminating the zerg as well. Across the End War the hybrid were deployed throughout the sector and had to be defeated piece by piece, but with the fall of Amon and the destruction of the breeding facilities, the hybrid were left largely annihilated. The known types included the destroyer and its dominator variant, the reaver and its behemoth form, and the Moebius, Nemesis, Prometheus, and Voidshade strains, while individual specimens such as Maar and the Castanar Hybrid were among the most dangerous the creatures ever produced. (StarCraft II: Wings of Liberty; StarCraft II: Legacy of the Void; StarCraft II: Co-op Missions)