Aiur witnessed the ebb and flow of protoss history, from the psionic race’s primitive origins to its accelerated evolution at the hands of the mysterious xel’naga. Eventually, due to growing antagonism among the protoss that led to the loss of their primal psychic link, the xel’naga left Aiur. The Departure, as this event was later known, caused protoss society to devolve into the most violent civil war ever recorded in galactic history: the Aeon of Strife. This conflict raged for generations, and during this period Aiur’s greater landmasses were devastated, and many of its lesser life-forms were pushed to the brink of extinction.
Although the xel’naga were gone, evidence of their presence remained on Aiur in the form of vast subterranean caverns and monolithic khaydarin crystals, some of which are present to this day. The eventual discovery of these strange xel’naga relics played a crucial role in ending the protoss’ brutal civil war. According to protoss legend, a mystic by the name of Khas had unearthed a khaydarin artifact, and through it he rediscovered the communal psionic bond that his race had lost prior to the Aeon of Strife.
Armed with this knowledge, Khas revitalized protoss society through the teaching of the Khala, a new theory that called upon the protoss to forgo their old feuds and reunite. As the protoss gradually embraced their ancient psychic link, they were flooded with the thoughts, emotions, and experiences felt by members of their entire race, thus tempering the hate that had fueled the Aeon of Strife.
In the centuries that followed, a golden age dawned on Aiur. Its war-torn continents were healed; its native species flourished; and numerous cities and temples were erected across its surface. The protoss population swelled to billions, and Aiur became the hub of an interstellar empire.
This period of stunning growth ended with the arrival of the Swarm. Intent on assimilating the protoss race, the rapidly mutating zerg eventually launched a full-scale invasion of Aiur. Led by a supreme sentience known as the Overmind, countless zerg overran the planet’s brave defenders and carved swaths of destruction across Aiur’s continents.
In a desperate act to save his people, the valiant former executor Tassadar made the ultimate sacrifice and set his ship, the Gantrithor, on a collision course with the Overmind. Although the resulting explosion annihilated the monstrous zerg entity, Tassadar’s heroic act failed to drive the rampaging zerg from the planet. Aiur was lost: the embattled remnants of protoss society were forced to abandon their revered homeworld. These refugees found sanctuary on the distant planet of Shakuras, homeworld to the dark templar, a group of rogue protoss who had long ago been exiled from Aiur for shunning the Khala.
Aiur has since come under the control of the Swarm’s new leader, the Queen of Blades. Some areas of the planet were left untouched by the invasion, but much of Aiur is now a zerg breeding ground littered with ash, broken war machines, and the remains of the dead. Scattered groups of protoss are rumored to exist on the planet, but their true numbers are unknown. The fate of Aiur’s other life-forms is also a mystery, and a small number of protoss speculate that some of these species have been assimilated by the zerg and mutated into killing machines to serve the Swarm.
For all of Aiur’s long and rich history, the planet is now commonly seen as a stark warning of the Swarm’s destructive power. Although the protoss once considered themselves the most advanced civilization in the galaxy, Aiur’s tragic fate has taught them a valuable lesson: they must be willing to adopt new tactics and allies if they hope to survive the chaotic era that has descended on the Koprulu sector.