Xel'naga

The xel'naga are an ancient, cosmic race. They helped the protoss and the zerg races to evolve. Following these experiments, the xel'naga were nearly destroyed by their own creation, the zerg, when the Overmind and its swarms launched an attack against them from the planet Zerus. There are vague references to them conquering many worlds and assisting other races to reach a higher level in their individual evolutions. The xel'naga were occasionally referred to as the most powerful species the universe has ever known.

The protoss have taken their architecture from the xel'naga, but there are also zerg and unique influences. Valerian Mengsk theorized from their temple at Nemaka that they were the progenitor race of both the protoss and the zerg.

History
The xel'naga came from beyond the Milky Way Galaxy, and were a psionically-attuned and highly advanced race. They had reached the ultimate stage of evolution and helped younger races evolve.

The xel'naga's primary intent was to engineer a being that possessed purity of essence and purity of form, and to this end they traveled the galaxy, altering many interesting species they had encountered. However, each time they met with failure.

Involvement with the Protoss
The xel'naga journeyed to the edge of the galaxy and to the huge engineered world of Aiur. Upon this world they discovered a psionic hunter race which would be known as the protoss, who displayed amazing strength, speed and resilience. The xel'naga took this to be a sign of purity of form. The species also had a unique psionic link. Seeing them as a successful creation, they were named protoss, meaning "first-born". The xel'naga secretly cared for them, and eventually, when they deemed it ready, revealed themselves to them. The site where they first set foot on Aiur was marked by a "protoss" temple which they constructed.

The xel'naga also constructed giant artificial caverns or city beneath Aiur, as well as hiding khaydarin crystals around Aiur.

The protoss united, fascinated by these new "gods." They called the xel'naga the Ihan-rii, and also called them the "Great Teachers", the "Makers", and the "Guardians". The Protoss Tribe that grew closest to the xel'naga during this time was the Shelak Tribe. During this period the Protoss underwent rapid technological uplift. Eventually, however, splits developed among the tribes as they struggled on decisions of what they should think of the xel'naga.

At first, the xel'naga were intrigued by this development, and conducted an experiment to see what effects the diverging tribes might have on Khaydarin crystals. They split twin crystals, giving one to the Akilae Tribe (named the Uraj) and one to the Sargas Tribe (named the Khalis). As the tribes diverged, so did the powers and even appearance of the crystals.

The xel'naga had worked to unite the protoss in one organization, but instead the tribes split and distanced themselves from each other. Indeed, the split was so severe it caused the disappearance of the psionic link. The xel'naga, knowing that they had pushed their creation too far too fast, set off from Aiur disappointed at their failure. The protoss, who felt betrayed, attacked the retreating xel'naga, killing hundreds. The majority of the Xel'Naga fleet sadly left Aiur and the protoss behind. The xel'naga left behind a single ship.

The protoss now had only themselves to turn upon, and suffered a kind of madness. This led to a stage of protoss history called the Aeon of Strife.

The New Beginning

 * Main article: The New Beginning

A protoss mystic named Savassan, from the Shelak Tribe, discovered the khaydarin crystals in a hidden xel'naga-crafted chamber on Aiur. With their power, he was able to slowly recreate the protoss psychic link. In addition, he searched for other xel'naga caches, discovering a large underground city.

Within the city, Savassan and his companion, Temlaa, discovered several desiccated "dead" protoss, all from different tribes, connected by organic wires to a very large crystal.

Savassan attached himself to the vines, and immediately began to wither, resembling the other "dead" protoss. Temlaa quickly used the console to free Savassan, who immediately began to heal, physically and mentally. Savassan said he and the crystal "shared things" and now he knew the path to healing. He learned that the Ihan-rii should be referred to as "xel'naga" and told Temlaa that "we don't need the xel'naga, we only need each other".

The protoss hated each other for driving the xel'naga away, but the real problem was hating their own flaws which had caused the loss of their communal link in the first place. Re-creating the link across the entire species would heal the madness and end the Strife, causing the protoss to feel each others' emotions. He called this theory the Khala.

Savassan, later known as Khas, traveled throughout the protoss settlements, introducing the protoss to the theory of the Khala. This brought about the end of the Aeon of Strife.

Numerous artifacts left behind by the xel'naga were used by the protoss, such as khaydarin crystals. The Conclave used the last remaining xel'naga ship as the basis of much protoss technology, and forbade entrance into the underground city.

Involvement with the Zerg
Having failed to create a race with the purity of form, the xel'naga now set out to create a race displaying only a purity of essence. To this end they used the zerg, a small insectoid creature from Zerus, as the base for genetic manipulations. The initial experiment was a resounding success. The parasitic zerg quickly became the dominant lifeform on the planet, with other creatures being assimilated and evolved or simply eliminated. The xel'naga were shocked to discover how quickly assimilated species could be changed beyond recognition within the space of a few generations.

In the view of the xel'naga, the protoss had failed due to the independence of the individual and conflicts of ego that arose from that. To avoid the same with the zerg, the xel'naga consolidated control of the collective zerg sentience into a single entity, the Overmind. The xel'naga used a psionic link with the Overmind to monitor the zerg, but the xel'naga kept the link secret as to not reveal their presence.

However, it was not long until the Overmind realized that to continue growing the zerg would need to leave Zerus, and assimilated the behemoths, enabling its forces to travel into space. It had since detected the xel'naga worldships in orbit and these made a logical first target for new material. The first sign that the xel'naga had that something was wrong was when the Overmind severed the psychic link. The zerg launched an overwhelming attack on the worldships. The "greater whole" of the xel'naga were slain and the Overmind assimilated some of the xel'naga's knowledge as it processed thousands of xel'naga into itself. Amongst other things, the zerg learned of the protoss, the other great experiment; they would become the zerg's ultimate target for assimilation.

Legacies
"The greater whole" of the xel'naga was annihilated by the zerg. Only ruins and artifacts remained, some functional, of the ancient race in and around the Koprulu Sector.


 * Main article: Xel'naga temple

The xel'naga have left behind many temples. On Aiur, they built a temple to mark the spot where they first set foot upon that world.

The xel'naga left a temple on Shakuras, sitting on a nexus of cosmic energy, where their marks (such as darkening the planet and a temple capable of mass destruction) are more obvious.

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.


 * Main article: Watch tower

In addition, watch towers seemingly crafted by the xel'naga have appeared.

Ara'dor
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.

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".

Return of the Xel'naga
Near the end of the Brood War, several characters have detected a vague threat associated with the xel'naga, associated with the completion of a "cycle", which will become more apparent in StarCraft II. Meanwhile, more artifacts (such as temples) have been unearthing themselves...

Kerrigan and Zeratul's Role
Infested 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.

Zeratul stumbled upon a shocking secret on a dark moon, where he discovered a protoss/zerg hybridization project overseen by the mysterious Samir Duran, who had previously appeared as an infested terran. Duran told Zeratul that Kerrigan was not in charge of his experiment, "although her rebirth into the Zerg Swarm has sped up my progress." Duran also told him that he was "a servant of a far greater power" and "this creature is the completion of a cycle. It's role in the cosmic order was preordained when the stars were young."

After her victory at Char Aleph, Infested Kerrigan was unable to shake the feeling that a great threat loomed just over the horizon.

Zeratul has gone through the stars in his spaceship, looking for clues to try to confirm the "cosmic event" that Duran told him about. He does find these clues and gets a vision of what's coming. On a lost world, he finds evidence of a prophecy of the xel'naga's return. But the question remains if they come to save, or destroy.

Zeratul appears on the Hyperion, command ship of Raynor's Raiders. Jim Raynor has been acquiring xel'naga artifacts to sell to the Möbius Foundation. Zeratul tells him that "the xel'naga return" and that the artifacts Raynor has acquired hold the key to the end of the cycle and the end of all things.

Zamara and Jake Ramsey's Reaction
The protoss preserver Zamara has also seen evidence of a cycle, although in her case, the evidence comes from the memories of the past that she holds, rather than from the present. She believes the secret involved a "pattern that had happened so often before and was about to happen again". The secret was described as "submerging and manifesting with a cold precision" and she knows (or has access to) the "horrific knowledge of what had come before, and what was certain to come again".

Zamara created a mind-merge with a terran, archaeologist Jake Ramsey, who now has access to this same information. In order for Ramsey to understand the nature of the threat, she showed him memories back from the Aeon of Strife. Meanwhile, several xel'naga artifacts have recently begun appearing around the Koprulu Sector after the emergence of the temple on Bhekar Ro.

Connections to Hybrids

 * Main article: Hybrid

Both the Overmind and Zeratul expressed the belief that the xel'naga may have approved of a union of protoss and zerg.

The xel'naga temple on Bhekar Ro was designed to absorb protoss and zerg essences, creating a strange "phoenix-like" creature which appeared to absorb the essences and genetics of both protoss and zerg.

Samir Duran's pronouncements on the hybrids being the "completion of a cycle" led Zeratul to seek out information on this new threat. Zeratul's discoveries convinced him that the xel'naga were returning to unleash doom upon the universe.

The Xel'Naga in StarCraft II
The xel'naga will not be a playable race in StarCraft II, as only the original three races can be played.

When Blizzard Entertainment employee Karune was asked if there would be any hybrid units in StarCraft II, he replied "we are planning to explore the mysteries surrounding the Xel'naga for the single player campaign. In the campaign you will encounter several unique units that would not otherwise be seen in multiplayer."

Chris Metzen has confirmed they will be part of the backbone of the StarCraft II trilogy.

The Möbius Foundation is very interested in alien artifacts and has hired Raynor's Raiders to locate them. However, Zeratul says that these artifacts are important in some way to the return of the xel'naga.