Keystone

The Keystone, also called the xel'naga artifact, was an ancient xel'naga relic and one of the major catalysts of the Second Great War. It could channel and redistribute energy, matter, essence, and consciousness in a multitude of ways, giving it many uses as the terran, zerg, and protoss studied it to their own ends. Sought by the Terran Dominion, the Swarm, and the Tal'darim alike, it de-infested Sarah Kerrigan, was secretly twisted toward the resurrection of Amon, and was ultimately used to banish him from the Khala.

Nature and design#

The Keystone was designed by the xel'naga to store the origin point of their primary temple at Ulnar, expressed in a unifying language any culture could interpret. It would store Void energy to reawaken the xel'naga when the chosen races, those that contained purity of essence and purity of form, arrived at the temple. Essence, matter, information, and consciousness could all be siphoned and redistributed within the relic and converted into energy, and the Keystone acted as a focal point between the material universe and the Void, converting the energies of one into those of the other.

The physical shape of the Keystone was a deception that allowed it to be realigned, and it had a decay rate higher than any normal construction material. Its construction resembled that of the temple of Ulnar, leading Phase-smith Karax to speculate that the two complemented one another. The relic was not inert even when separated, and its individual components could be located by their radiation emissions. It drew energy like a dry sponge, reacting that way with devices such as an ihan crystal, and it was capable of generating a powerful energy nova lethal to the zerg yet harmless to terrans, who heard only a subsonic pulse.

Though most relics were millions of years old, the first recovered component appeared to be only a few thousand years old, while pieces sealed in temples elsewhere were millions of years old. This was traced to the Keystone's self-repairing nature, and it was found that the relic actually predated most xel'naga artifacts by billions of years. Karax speculated it might have been the first object the xel'naga created upon entering the universe. Assembled, the entire device was slightly longer than a man is tall.

The scattered components#

Per the Infinite Cycle, it was intended that the chosen races would find and assemble the Keystone, which would guide them to Ulnar, the resting place of the xel'naga. The relic was divided into five components and stored separately in and around the Koprulu sector. By the Second Great War one was buried on Mar Sara, one lay in a Tal'darim-guarded shrine on Monlyth, another in a shrine on Typhon XI, and another was sealed in a xel'naga temple on Xil. The final piece was stored in a vault aboard an abandoned xel'naga worldship stranded in the Sigma Quadrant.

The race for the artifact#

During the Second Great War the terrans, zerg, and protoss all took an interest in the device. Crown Prince Valerian Mengsk covertly sought it through the Moebius Foundation, intending to de-infest the Queen of Blades and strike a decisive victory against the zerg, expecting the feat to settle any question of his fitness to succeed his father, Emperor Arcturus Mengsk. Sarah Kerrigan was likewise interested, driven by a growing understanding of the coming of Amon and his hybrid, and the Swarm prepared a sector-wide invasion to recover the relic. The Tal'darim, familiar with the locations of most components, viewed them as holy relics and appointed themselves their guardians. Emil Narud, aware of the Keystone, planned to use it to revive Amon without informing the Tal'darim.

A sanctioned Dominion expedition had finished excavating the Mar Saran component just before the war, and the Moebius Foundation hired Raynor's Raiders, through Tychus Findlay, to obtain it, in contravention of a Dominion ban on the trade of alien artifacts. The Raiders retrieved the piece just ahead of the Swarm's attack on the dig site and escaped aboard the battlecruiser Hyperion. The Foundation then directed them to Monlyth, to a xel'naga temple on Xil, and to Typhon XI, where the imminent supernova of the local star complicated the operation, each time pitting them against the Tal'darim and the zerg. Kerrigan, recognizing the Moebius Foundation as the source of the Raiders' success, attacked its headquarters on Tyrador VIII, and the final component was recovered from the derelict xel'naga worldship in the Sigma Quadrant.

The Battle of Char#

Bringing the assembled device into range of Sarah Kerrigan required the terrans to invade Char. Valerian Mengsk assembled half the Dominion fleet under General Horace Warfield, and the Raiders joined the battle group. Though the terrans suffered heavy casualties, they established a foothold and crippled part of the zerg defenses, bringing the Keystone to the base of the main hive and digging in around it. The Queen of Blades personally led the attack, but the terran defenses held and the fully charged device eliminated the nearby zerg and partially de-infested Kerrigan, altering her DNA by extracting the energy the Overmind had used to transform her years earlier. Unknown to the terrans, that energy was not dissipated but stored within the Keystone as part of Narud's plan to resurrect Amon, and Kerrigan suspected the energy had been gathered by nearby hybrid.

Narud's betrayal and the death of Mengsk#

Jim Raynor brought Kerrigan onto Valerian Mengsk's flagship Bucephalus, and in fleeing Dominion justice the two became rebels. Emil Narud joined them, proclaiming the device a weapon and insisting its de-infestation of Kerrigan had not been an intended function. Both Kerrigan and the device were brought to the secret Moebius Foundation station Prometheus, but Narud betrayed the rebels to Arcturus Mengsk and escaped with the relic aboard a warp-capable transport.

The device was later installed as a security measure in the emperor's office on Korhal, its remote control disguised as a lighter. When Kerrigan, by then transformed once more, attacked the palace and confronted Arcturus Mengsk, he used the Keystone to subdue her, until Raynor intervened and destroyed the remote. Kerrigan then killed the emperor.

The banishment of Amon#

Guided by Zeratul's advice, Hierarch Artanis and his forces went to Korhal to retrieve the device for the war against Amon, fighting through Moebius Corps forces and enduring the devastating mental pulses the Keystone unleashed when charged with Void energy. Once it was recovered, Phase-smith Karax studied it and discovered the location of Ulnar within the Altarian Rift, learning that the relic redistributed essence, matter, consciousness, and energy and had been modified from its original purpose. He theorized it could extract Amon from the Khala and so save the afflicted protoss from his corruption.

On the Tal'darim homeworld of Slayn, the Keystone reacted to the planet's Void energies, and Karax used terrazine drawn from the world to test its capacity for Void energy. Artanis then brought the relic to Aiur, where it radiated a red glow in reaction to Amon's presence, and Karax warned that he did not know how long it could hold the essence of a xel'naga. It was deployed on the surface after the destruction of Amon's host body. Amon sent all his forces, zerg, hybrid, and the delayed Golden Armada, to destroy the device, but the unified protoss held a defense around it long enough for it to gather the energy needed to pull Amon from the Khala. As the artifact activated, Artanis convinced Executor Selendis and the remaining Khalai to sever their nerve cords, leaving Amon no place to flee. He was forced back into the Void, and the Keystone was destroyed in the process.