Xel'naga

"The Xel'Naga created both the protoss and the zerg, Commander. They were the gods of their time."

- Doctor Emil Narud

The xel'naga are a highly advanced race.

Described as "the most powerful species the universe has ever known," the xel'naga have been referred to as "wanderers from afar," but it has also been described as being their true name. The protoss referred to the xel'naga as the "Ihan-rii", the "Great Teachers", the "Makers", and the "Guardians", during the Aeon of Strife, and prior to it, worshipped them as gods. Some protoss still refer to them as such.

According to protoss tradition, the xel'naga were peaceful, benevolent and utterly consumed with studying and propagating sentient evolution within the universe.

Origins
The xel'naga were incredibly long-lived even by protoss standards, but not immortal; eventually their species would come to an end. In the interest of survival they planned to create new xel'naga by uplifting two species. A pair of qualities was required and these were defined by the xel'naga as the purity of essence and the purity of form, and each uplifted species would be targeted for one of them. Over an extraordinarily long period of time, the two species would naturally come together and merge, forming the next generation of xel'naga and beginning the cycle anew. The xel'naga life cycle has manifested many times, so often that time itself was affected by it.

Arrival in the Milky Way
The xel'naga were not indigenous to the Milky Way galaxy, but ruled over thousands of worlds within it, tens of millions of years before the Great War. It was rumored that they seeded and cultivated thousands of various species on these worlds. They became obsessed with fashioning the perfect life-form and labored to create a creature that would be defined by what they termed 'a distinct purity of form'. Using khaydarin crystals, they carefully steered the delicate evolutionary processes of their budding species for millennia, keeping a detailed genetic history of each race. Their protracted experiments produced many intriguing deviants and mutations, but the races that they cultivated always fell short of their enormous expectations.

During their journeys, they learned of the Voice in the Darkness, a Void-based entity which consumed entire civilizations. The xel'naga, who cherished life, imprisoned it with an Argus crystal beneath a barren world at KL-2.

The xel'naga found or created a powerful relic, the Argus Stone, which they valued over other artifacts, but left it on the world of Aridas. The zerg believe it had been used to create entire races.

The Firstborn
"You worship false gods, little protoss, but now the truth stands revealed. You were never master of your own destiny...never more than a pawn in the xel'naga's cosmic game."

- The Voice in the Darkness

Still driven to perfect their science of proto-genetic evolution, the xel'naga focused their frustrated efforts on Aiur, one of their engineered worlds. Pleased with the progress of its most advanced native life-forms, the xel'naga conceded that their latest creation was their first of all their experiments to evolve beyond the feral constraints of baser life-forms. They gave the new race the name of protoss, or 'the firstborn'. Unsatisfied with their slow progress, the xel'naga accelerated their evolution and spent a millennium subtly guiding their steps. They even used devices such as the Kassia crystal to enhance their rate of reproduction. Eventually, the xel'naga succeeded in leading the protoss to the state of total sentience and awareness. When the protoss became highly intellectual and introspective, the xel'naga were exhilarated by their seeming success. Attempting to discern the full extent of protoss evolution, the xel'naga made themselves known to the protoss and integrated into their culture.

The xel'naga constructed a temple to mark the site where they first set foot upon Aiur. They also dug vast subterranean caverns.

The protoss were united by their fascination with these new "gods." They called their new benefactors the Ihan-rii, the "Great Teachers", the "Makers", and the "Guardians". The xel'naga marveled at how driven the protoss were to plumb the mysteries of the universe around them. However, they reeled in frustration when the protoss tribes grew further and further apart. At first, the xel'naga were intrigued by this ideological development, and conducted an experiment to see what effects the diverging tribes might have on khaydarin crystals. They created twin crystals, the Khalis and Uraj, from a monolithic crystal and gifted them to the Sargas and Akilae Tribe respectively. The crystals' powers and appearance diverged with their tribes.

The Departure
The xel'naga speculated that perhaps they had pushed protoss evolution too far. As individual egos arose to overpower the once primary communal link, many xel'naga believed that the protoss had lost their greatest strengths. With the loss of the primal psychic link, which the xel'naga considered the most fundamental element of their greatness, they deemed that the purity of form they sought to create had been sullied by a conflict of essence and thus decreed that the protoss were a failed creation as a result of their sentience being pushed too quickly. The xel'naga were already done with the protoss, and needed to work on a new species. Hundreds of xel'naga were killed in a protoss attack, but they were fended off long enough for the greater number of their worldships to be launched into the void. They left behind khaydarin crystals and at least one ship.

Broken Cycle
"Would-be gods who defied the natural order at every turn. Though in the end, the xel'naga's hubris brought naught but ruin...upon themselves and all they touched."

- The Voice in the Darkness on the xel'naga's downfall.

The xel'naga traveled to Zerus, where they dismissed their tenets of physical form and focused chiefly on the pursuit of a distinct purity of essence. They labored to advance the evolution of the zerg, which was the most insignificant life form on Zerus until xel'naga proto-genetic manipulations enabled them to survive the torrential firestorms and thrive.

The xel'naga were alarmed to discover that the original races assimilated by the zerg were almost unrecognizable after only a few generations of their inception.

Remembering their failure with the protoss, the xel'naga attempted to waylay the potential hazards of differing egos by structuring the collective sentience of the zerg into a unified, amalgamated 'Overmind'. They kept a constant watch on the Overmind via a psychic link. Amon desired their ability to steal essence, but the zerg were independent, so he bound them to the hive mind.

The xel'naga knew that they had achieved their goal when the zerg became conditioned to survive the harshness of space. However, they were horrified to discover that the Overmind had actually severed their psychic link, effectively severing itself from their view. When the Swarm was launched at the xel'naga fleet, they attempted to stem the tide of the ever-advancing onslaught. Despite this, the reinforced hulls of their worldships were battered by wave after wave of zerg swarms with no signs of abatement. The xel'naga defenses were overrun within a few hours and the greater whole of the xel'naga race was consumed, an action which threw the xel'naga plan into turmoil.

The Overmind assimilated some of the xel'naga's knowledge as it processed thousands of xel'naga into itself. Amon gave it a directive to destroy the protoss, as part of a plan to remake the universe in his name. The protoss became the zerg's ultimate target.

Creation's Vacuum
"This creature is the completion of a cycle. Its role in the cosmic order was preordained when the stars were young. Behold the culmination of your history."

- Samir Duran

After Amon died, the zerg continued to feel his influence and his servant tried to resurrect him for millennia.

During the Golden Age of Expansion, Khyrador became home to the Uraj crystal. However, it was later abandoned when a series of violent psionic storms rocked Khyrador and drove away its protoss settlers.

Believing terrazine to be a gift from the xel'naga, Tal'darim mystics set up altars on Bel'Shir to collect what they called 'the Breath of Creation'. The Tal'darim also guarded pieces of a xel'naga artifact on Monlyth, Xil, Typhon XI and a derelict xel'naga worldship in the Sigma Quadrant. When the Dark Templar found a temple which the xel'naga had constructed above a nexus of powerful cosmic energies, they decided to remain on Shakuras to study it. During the Brood War, the temple grounds were infested by two cerebrates. The protoss scoured the infestation then secured the Uraj. On Char, several cerebrates locked onto the Khalis' energies and nested near it, but it too was retrieved by the protoss. The protoss used the crystals to channel the temple's energies. The resulting explosion obliterated the zerg on Shakuras.

Shortly before the, the xel'naga temple on Bhekar Ro was unearthed. The temple housed a strange "phoenix-like" energy creature which absorbed the essences and genetics of both protoss and zerg.

Samir Duran used genetic manipulation to create protoss/zerg hybrids on a thousand different worlds. At the end of the Brood War, Dark Prelate Zeratul encountered Duran on a dark moon. He continued to seek answers for what manner of being Duran truly was, and what dark future he was working toward. However, he was suffering mentally for numerous reasons, such as the death of Matriarch Raszagal at his hand. Years after his discovery, Zeratul was located by a preserver, Zamara, and her terran "host", Jake Ramsey. They restored Zeratul's mood and exchanged information. According to Zamara, Samir Duran's experiments are a "perversion", and if his attempts to "unify" the species become successful, "a monstrous and powerful perversion of both protoss and zerg will be set loose upon the universe, and all that [the protoss and terran] know and cherish will fall in their wake".

Zeratul traveled to the world of Pegasus, where a xel'naga temple hatched. He followed the energy creature through a wormhole to a mysterious planet on the other side.

Return of the Xel'naga
After uncovering a revelation somehow related to the xel'naga, Zeratul sought additional clues to unravel the mystery. Both he and Sarah Kerrigan were drawn to Ulaan to uncover a prophecy, rumored to foretell the return of the xel'naga, that was divided into three fragments, each kept at separate shrines. Zeratul gathered the fragments and had them deciphered by the preservers of Zhakul.

Crown Prince Valerian Mengsk used the vast resources of the Terran Dominion to scour the Koprulu sector for xel'naga artifacts. His Moebius Foundation sought the artifact which by this point was a few thousand years old.

The Dominion went to Mar Sara to excavate a piece of the artifact. For months, Dominion engineers excavated it at White Rock Base. The Dominion forcibly shipped citizens there from Backwater Station to dig it up. As they were getting ready to move the artifact off-world, it was seized by Raynor's Raiders.

Fearing the artifact's power, Kerrigan dispersed the zerg to search for the various pieces. After Raynor's Raiders had collected the other artifact fragments, it was assembled and the engineer corps moved it to the base of the primary hive cluster on Char. The terrans protected the artifact while it charged. Commander Jim Raynor and General Horace Warfield used it to make Kerrigan human again. Nearby hybrid gathered the psionic energy she wielded as the Queen of Blades, giving Emil Narud enough energy to resurrect Amon.

The xel'naga wished Kerrigan restored as leader of the Swarm, and had Zeratul (by this point serving their interests, or at least what he perceived as the greater good) guide her to Zerus, where she was reborn as the Primal Queen of Blades, free of Amon's influence. Xel'naga relics which housed genetic information were also collected by Kerrigan on Zerus.

Narud battled Kerrigan at Amon's temple, which he had built Skygeirr Station on top of. Alexei Stukov deactivated the five xel'naga temples that were amplifying Narud's power. Kerrigan killed Narud in the heart of the temple, but by this point Amon was alive again.

Culture
The xel'naga cherished all life and refused to kill anything, not even the entity at KL-2. The protoss eventually followed a version of this philosophy, called the "Dae'Uhl".

At least some xel'naga buried and/or entombed their dead.

The xel'naga used a "universal natural" code the protoss termed "ara'dor", which means "perfect ratio". Terrans call it the Golden Mean, symbolized by φ ("phi").

In mathematics and the arts, two quantities are in the golden ratio if the ratio between the sum of those quantities and the larger one is the same as the ratio between the larger one and the smaller. The golden ratio is approximately 1.6180339887. The golden ratio is related to the Fibonacci sequence and the Golden Spiral.

Technology
The xel'naga left numerous artifacts on Aiur and other worlds, such as Ehlna, Roxara and Aridas.

Some artifacts can be considered dangerous, since they can manipulate the minds of terrans. At least some are alive in a sense (once being described as an "energy fossil").

These artifacts are sought by protoss. The Dark Templar especially have made efforts to track these down.

The Terran Dominion made attempts to buy some from rival powers. Even the zerg have used spies in an effort to locate artifacts.

Still more temples have appeared on worlds such as Nemaka, Aridas (where the powerful Argus Stone was stored) and Bhekar Ro; the latter disgorged a strange energy creature which collected protoss and zerg genetics for unknown purposes.

Valerian Mengsk, the Heir Apparent of the Terran Dominion, has expressed interest in these temples, and Dominion forces have engaged in combat in an attempt to secure such temples.

Watch towers seemingly crafted by the xel'naga have appeared.

The xel'naga possessed the ability to create space platforms.

Prophecies
"Now, the Xel'Naga that forged us all, are returning. But do they come to save, or to destroy?"

- Dark Templar Prelate Zeratul

Braken Prophecies
There are prophecies relating to the planet Braken, a protoss world with religious significance. These prophecies claim that "he who harnesses this world will someday wield a great power, sanctified by the ancient ones".

Kerrigan and Zeratul's Role
Kerrigan bantered with Zeratul on Char as a prelude to combat, where Zeratul told her: "Your coming has been foretold... You are part of the culmination. But not the end of it. You shall show the way, the path that must be taken, the realigning of old truths no longer valid. Yours is not the hand, but your very existence provides necessary instruction." Kerrigan did not treat the pronouncement seriously at the time.

Xel'naga Worlds
The following are worlds known to have been visited by the xel'naga, many of them possessing relics of their presence:

Known Xel'naga

 * Amon (a 'fallen' xel'naga)
 * Samir Duran
 * Sarah Kerrigan (through essence transfer)
 * Ouros

Development
During development the hybrid destroyer was known as a xel'naga destroyer.

A development version of the map Echoes of the Future identifies the xel'naga as the ones who manipulated the Overmind to destroy the protoss: Overmind: The Xel'Naga had created me to eradicate their failed children - the protoss - in a battle neither species would survive. The Overmind also created Kerrigan to stop the return of the Xel'naga: ''Overmind: Yet my...daughter...remained. She alone would break the cycle. She alone would forge a future devoid of the hated Xel'Naga.''