1 – "Golden Orb of Day"
At least third
24 standard hours 
+/- 30º Centigrade [86 Fº], high humidity
Jungle, ruined jungle
Zerg infested world
Aiur is the protoss homeworld, located in a star system with a single yellow star and possessing a single moon not unlike Luna. It is at least the third of the system's terrestrial planets, if not further out.
A great psionic matrix emanates from Aiur. Protoss structures and units, to a lesser extent, draw their energy from it. A nexus provides a link to this matrix, but pylons are needed to actually tap into the energy required to provide psionic energy to new colonies.
Aiur's moderate greenhouse-gas levels and low orbital eccentricity allowed it to develop a climate conducive to life. Over the eons, its humid rainforests teemed with a variety of species, the most advanced of which were the protoss, whose evolution was accelerated by the xel'naga. In addition to digging vast subterranean caverns, the xel'naga constructed a temple to mark the site where they first set foot upon Aiur.
The xel'naga eventually left Aiur due to growing antagonism among the protoss that led them to forget how to attune themselves to their primal psychic link. This led to the Aeon of Strife, during which Aiur's greater landmasses were devastated and many of its lesser life-forms were pushed to the brink of extinction.
Eventually, Khas unearthed khaydarin crystals left behind by the xel'naga. He channeled their primal energies through himself and rediscovered the communal psionic bond of the protoss. Khas revitalized protoss society through the Khala, which called upon the protoss to forgo their old feuds and reunite. Gradually, the protoss embraced their psychic link and were flooded with the thoughts, emotions, and experiences felt by every protoss.
The following centuries saw a golden age on Aiur. Its war-torn continents were healed; its native species flourished; and five cities and thirty-eight temples were erected across its surface. The protoss population swelled to billions, and Aiur became the hub of the Protoss Empire.
A group of rogue protoss shunned the Khala. The Conclave ordered Adun to eradicate them, but instead he attempted to convince them of the Khala's truth by teaching them how to manipulate their own latent psionic powers. Without the Khala's discipline, their powers spiraled out of control and unleashed psionic storms across Aiur. The Conclave banished the rogues from Aiur and they became known as the Dark Templar.
In 2500, the zerg launched a full-scale invasion of Aiur. The protoss defenders were overrun and countless zerg carved swaths of destruction across Aiur's continents. They seized the khaydarin crystals and destroyed the xel'naga temple before setting the khaydarin crystal in its place, allowing the Overmind to embed itself in Aiur's surface.
Praetor Fenix fought against the zerg but was hampered by the ability of their cerebrates to reincarnate. He was also held back by the incompetent leadership of the Conclave, the protoss governing body.
When former Executor Tassadar, a veteran of previous battles of the zerg who had turned rebel, returned to Aiur with Dark Prelate Zeratul, Judicator Aldaris attempted to arrest them. Tassadar's followers destroyed the Heart of the Conclave.
With the help of the renegade terrans of Raynor's Raiders, Tassadar and his followers weakened the Overmind, sustaining heavy losses in the process. Tassadar channeled Dark Templar energies through the hull of the Gantrithor and steered it on a collision course with the Overmind, destroying it. However, the zerg invasion left much of Aiur in ruins. The Conclave and nearly seventy percent of the population was killed. Aldaris, Fenix, Zeratul and Commander Jim Raynor banded together in order to unite and lead the scattered survivors, but the zerg continued to slaughter every protoss they encountered.
At Zeratul's suggestion, the Khalai survivors retreated to their last functional warp gate, fighting through a sizable zerg force to get there. Fenix and Raynor held back and protected their flank while the Khalai survivors escaped to Shakuras. Hundreds of thousands of protoss died during the evacuation. Some protoss were stranded on Aiur, and some observers remained behind to keep watch.
The zerg took control of the gate, but Raynor and Fenix retook it and shut it down to prevent the zerg from sending more reinforcements to Shakuras. Praetor Artanis sent though all the troops he could spare.
After being contacted by Sarah Kerrigan, Raynor brought Emperor Arcturus Mengsk, fleeing from the United Earth Directorate, to Aiur. The warp gate was activated and Fenix's troops held off the zerg who were incited to attack by its energies. Raynor's command center was destroyed by UED troops, but Lieutenant Samir Duran, supposedly a UED colonial officer, moved his forces out of place and the zerg intervened, allowing Mengsk and Raynor to escape through the warp gate while the UED retreated.
The protoss refugees on Shakuras made at least one trip to Aiur to recover wounded protoss warriors. Protoss commanders noticed stranded protoss but, believing they could not be rescued, kept their existence secret.
Around 2503, the zerg occupiers had stopped fighting each other, but had stopped spawning and continued to wander the planet like "discarded tools".
The stranded protoss divided into two factions—Shel'na Kryhas and Tal'darim— and clung to life on the ruined world, fighting and avoiding conflict with the zerg. The arrival of a preserver, contained within the brain of terran archaeologist Jake Ramsey, brought great changes to both groups of protoss. The former attempted to flee through the disabled (and then repaired) warp gate, while the latter splintered as they learned the truth behind their mysterious Benefactor. The Shel'na Kryhas and renegade Tal'darim banded together to attack the Benefactor, most giving up their lives using a powerful psionic technique to hold the Benefactor off.
Some of the renegade Tal'darim escaped but none of the Shel'na Kryhas made it. The remaining Tal'darim were attacked by zerg forces led by Ethan Stewart, who was seeking to use the gate and then find Ulrezaj. Ulrezaj absorbed some of his own followers to recharge his power before leaving in a xel'naga vessel, pursued by the zerg and Dominion.
Aiur came under Kerrigan's control. Although some areas were left untouched by the invasion, much of Aiur became a zerg breeding ground littered with ash, broken war machines, and the remains of the dead. A small number of protoss speculated that some of Aiur's other life-forms had been assimilated by the zerg and mutated into killing machines to serve the Swarm.
This article or section contains information about StarCraft: Ghost, which has been declared non-canon. Elements may be taken as 'flavor lore' however.
Echoes of the FutureEdit
In 2504, Zeratul returned to Aiur to learn the Overmind's secrets by making contact with the tendrils connected directly to its cortex. There he encountered the spirit of Tassadar, who revealed that the directive to destroy the protoss was forced upon the zerg and that Kerrigan was the only one who could free the zerg from slavery.
This article or section contains information from StarCraft II: Legacy of the Void.
The content may change substantially over time.
In 2505, the Golden Armada launched an invasion of Aiur in an effort to retake it for the protoss. A massive army landed outside a city and pummeled its way in. They then fought the zerg at a temple and activated three generators. However, the invasion went awry as Amon revealed his presence, corrupting the Khala and forcing Artanis to lead his remaining forces in retreat.
Aiur is a planet high in biodiversity and has a large variety of flora and fauna. Known species include;
- At least one species of bird
- Various aquatic species about the size of leeches.
- Mendella (ruins, replaced by a proving ground)
- Brushfire Island
- Cave of Relics
- Eldritch Lake
- Garden of Aiur
- River of Light
- Road of Remembrance
- Shreka Hills
In the StarCraft II map editor, there exists a map of Aiur, showing the spread of creep across its surface. However, apart from the creep spread, this map is identical to one of Bel'Shir, so assessing its validity is difficult.