The Protoss are a sentient humanoid race native to Aiur. They are technologically advanced and rely on psionic abilities and cybernetics in battle. They are the primary opponents of the Zerg. The Protoss of Aiur are highly religious and follow a strict code known as the Khala. The Protoss have mastered their psionic powers and were recently engaged in a devastating war with the Zerg. They have also had to deal with civil wars within their ranks. Protos in Greek means 'first'. This name is supposedly given because the Protoss were the first semi-successful Xel'Naga creation. The Protoss were later deemed a failure by the greater species, leading to the engineering of the Zerg.
The Protoss were discovered by the Xel'Naga on Aiur, a world the Xel'Naga had previously engineered. The Xel'Naga, who were nearing the end of their life cycle, were in need of a race to achieve purity of form and intrigued by their mental connection, chose to use the Protoss. Pushing the evolution of the Protoss, the purity of form was achieved and the Xel'Naga eventually descended to Aiur. The Protoss, who revered the Xel'Naga as gods, learned much from them. However, these discoveries divided the Protoss, causing their psychic links to disappear and wars to break out amongst them. The Xel'Naga left the planet as the Protoss fell into the Aeon of Strife. The destructive civil war ended when Khas, using Xel'Naga-derived artifacts called khaydarin crystals, re-created the psionic link. It became the basis of a new philosophy called the Khala.
Approximately 1500 by Terran reckoning, the Conclave attempted to exterminate rogue heretics who had deliberately cut themselves off from the Khala and would later become known as the Dark Templar. They ordered Executor Adun to execute them, but Adun refused, instead teaching the rogues to hide from the Conclave. Eventually the rogues lost control of their powers, alerting the Conclave. They were secretly banished on a Xel'Naga ship.
By 2499 the Protoss became aware of a xenomorphic threat, the Zerg, another alien species also created by the Xel'Naga. The Zerg were attacking the Terrans, a species which had traveled to the Koprulu Sector two hundred years previously. The Conclave dispatched Tassadar and a force of Protoss to destroy the infestation by purifying the infested worlds.
Fall of Aiur
Tassadar's force failed in its mission, and the remnants traveled to the new Zerg homeworld, Char. There, Tassadar struck an alliance with the Dark Templar prelate, Zeratul. They discovered a weakness in the Zerg command structure which could be exploited only by the Dark Templar, and clashed with their new leader, Infested Kerrigan. Meanwhile, the majority of the Zerg force traveled to Aiur. The Protoss were losing the battle, but when Tassadar brought Zeratul to Aiur, a Protoss civil war broke out between Tassadar's followers and the followers of the Conclave. Eventually Tassadar's faction won. Unimpeded by the Conclave, Tassadar's followers attacked the Overmind itself. Tassadar died during the battle. The majority of Protoss on Aiur were killed. The Protoss fled to Shakuras, followed by a Zerg faction. The Protoss destroyed the renegade Zerg, saving themselves but advancing Infested Kerrigan's aims. With the assistance of her enigmatic minion Samir Duran, she would later force the Protoss into destroying the second Overmind for her, making her the sole leader of the Zerg Swarm. As the Protoss attempted a revenge strike on Kerrigan, Duran abandoned her to conduct Protoss/Zerg hybridization experiments, which were discovered by Zeratul. The latter exiled himself for several years following the discovery.
Unique aspects of the Protoss units include
- Pylon (power supply, a unique ability which causes structures (and/or units) to become enabled/disabled)
- All Structures (power user, the second part to the Power ability. Units with this ability are deactivated unless within a Power radius)
- Mothership - Cloaking Field (unique aura which applies a 'cloaked' buff to all friendly units and structures
- Stalker - Blink (a short distance teleportation spell)
- Nexus - Chronoboost (a buff which speeds up a friendly structures construction queue by 50% for 20 seconds.
http://starcraft.wikia.com/wiki/Protoss for most of the text.