The protoss are a sapient humanoid race native to Aiur. Their advanced technology complements and enhances their psionic mastery. The main protoss cultural groups are the Khalai, who adhere to the communal Khala, and the Nerazim, who reject the Khala. In addition, another branch of the protoss separate from the Khala called the Tal'darim lives in various places in the galaxy.
Protoss civilization was reunified when the Khalai and Nerazim, sundered since the Discord, were reunited after the devastation of Aiur by the zerg during the Great War.
Alongside the zerg and terrans, the protoss stand as one of the three dominant species of the Milky Way.
Protoss are about three meters tall and have two glowing eyes, digitigrade legs, semi-permeable skin covered in scales, four digits on their hands (of which two are thumbs) and toes, broad chests and shoulders, and narrow waists with slim midsections. Extending back from the crown of the head, protoss have a bony crest. Beneath it, emerging from the back of the head, are the nerve cords, allowing them to access their racial psionic gestalt. This gestalt is the basis of the Khala. The xel'naga considered these beings to have purity of form as the protoss are incredibly adaptable to harsh natural conditions and climates, and their strength and speed were unparalleled amongst the other races known to the xel’naga. Protoss even have sharp claws, which can be deadly weapons if a protoss is caught unarmed.
Protoss derive sustenance from light, capable of living off of moonlight (reflected sunlight), and can go without light for extended periods of time. What little water they need is absorbed through the skin. The Dark Templar modified themselves biologically and used other techniques to survive on the formerly lightless world of Shakuras.
The protoss used to hunt, but they did so to collect the blood and hides of animals for various purposes, not for sustenance.
Protoss hear and smell through their skin, and it is believed that their primary sense is sight. Protoss have a sense of smell sharp enough to identify other protoss and see very well at night. A protoss' skin color may change in response to changes in its emotions. They are bereft of mouths, noses, or visible ears and are without a sense of taste. They possess three hearts.
Protoss sleep and dream in a manner similar to humans.
A protoss' average life expectancy is lengthy; Raszagal, aged 1045, was considered old. Protoss under 300 years rarely have any significant political positions. Artanis, who was 262 years old during the Brood War, is considered young, despite his powerful military position.
Protoss are not a prolific people and the xel'naga even developed an artifact, the Kassia crystal, to counteract this. The population of Aiur, however, had reached billions. Before the Fall of Aiur, the protoss population was in decline due to systematic extermination; the protoss were passing away from sheer age.
Protoss blood is blue or purple. As in humans, coloration is considered a sign of ethnicity, with each protoss tribe having a specific subtly differing hue or typical pattern of markings associated with it.
As with terrans and zerg, protoss genetic material consists of DNA with helix strands. There is evidence that the protoss have yet to unlock their full genetic potential, but this theory died along with the Protoss Advance/Experimental Facility.