Keystone

"As we have seen, the Keystone was designed to be found and assembled by those who would ascend to become xel'naga. After leading them to Ulnar, it would also expel its stored energy to awaken the slumbering xel'naga. The Keystone siphons energies and redistributes. Essence, matter, information, consciousness...to this device, they are all the same."

- Phase-smith Karax

The Keystone was one of the major catalysts of the Second Great War. An ancient xel'naga relic, it could channel and redistribute energy, matter, essence and consciousness in a multitude of different ways, giving it myriad uses as the races studied it to various ends.

Overview
The Keystone was not inert even when separated. The individual components could be located by their radiation emissions.

While stored in Hyperion's, Egon Stetmann noticed that as more components were collected and stored together, the more power the containment field required. According to Commander Jim Raynor, the battlecruiser's crew claimed to have been experiencing strange visions and unexplained noises, though Doctor Ariel Hanson dismissed them as superstitious nonsense – suggesting that she herself had not had such experiences.

The Keystone draws energy like a "dry sponge". It reacts that way with devices such as an ihan crystal. It was said by terrans to be able to drain the energy out of a protoss, and kill a protoss just by being in close proximity to it. The Keystone can also generate a powerful "energy nova" that is lethal to zerg. This nova pulses on a subsonic frequency harmless to terrans.

The Keystone was considered a weapon by Doctor Emil Narud, who said its ability to absorb protoss and zerg DNA would be a natural weapon for the xel'naga. He also said its ability to de-infest an infested terran (Sarah Kerrigan) was not the way the designer intended the device to be used. It later was discovered that this was a modification done by Narud himself in an attempt to revive his master, Amon.

The Keystone is unique in xeno-archeological terms in that by the early 26th century, the first piece (recovered from Mar Sara) appeared to be only a few thousands years old, while most relics are millions of years old. Some of the pieces acquired later in the war (such as on Xil) were sealed inside temples that were millions of years old. This was discovered to be due to the self-repairing nature of the Keystone, and that it actually predated most xel'naga artifacts by billions of years. Phase-smith Karax speculated that it may have been the first object created by the xel'naga upon entering the universe.

The physical shape of the Keystone is a deception, allowing the Keystone to be realigned. The Keystone itself has a decay rate higher than any normal construction material.

When combined, the entire device is "slightly longer than a man is tall".

History
"So beautiful, for a weapon." "Weapon? So you know what it's for?" "To the xel'naga, who extensively modified both the protoss and the zerg, being able to destroy their DNA would naturally be a weapon. That terrans found a way to employ it for a positive end result had nothing to do with the designer's intent."

- Emil Narud and Jim Raynor discussing the artifact.

Antiquity
The Keystone was created by the xel'naga at the dawn of the universe's creation. 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 Keystone 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 was in a Tal'darim-guarded shrine on Monlyth with another in a shrine on Typhon XI, and another sealed in a xel'naga temple on Xil. The final piece was stored in a vault aboard the abandoned xel'naga worldship stranded in the sigma quadrant.

Pawn of Power
During the Second Great War, the terrans, protoss, and zerg took an interest in the device.

Crown Prince Valerian Mengsk of the Terran Dominion covertly sought the device through the Moebius Foundation. He intended to use it to deinfest the Queen of Blades, and strike a decisive victory against the zerg. The prince expected such a feat to end any question of his abilities, and his suitability to succeed his father, Emperor Arcturus Mengsk. The Foundation's research effort was based on Tyrador VIII.

Kerrigan was also interested in acquiring the Keystone. The Queen of Blades was driven by a greater understanding of the forces at work in the galaxy and the coming of Amon and his hybrids. The zerg prepared to launch a massive Sector-wide invasion to search for and recover the device.

Of all the interested parties, it was the Tal'darim, a protoss sect, who were actually familiar with the locations of most of the components. They viewed the components as holy relics and appointed themselves guardians against all thieves. Emil Narud was aware of the Keystone, and planned to use it to revive Amon. However, he did not inform the Tal'darim of his plans.

Stealing from the Dominion
An officially sanctioned Dominion expedition completed excavating the Mar Saran component just before the Second Great War after months of digging. The Moebius Foundation hired Raynor's Raiders, through Tychus Findlay, to obtain the components, starting with the Mar Saran piece. This was in contravention to an official Dominion ban on the trade of alien artifacts.

The Raiders retrieved the component just ahead of the Swarm's attack on the Dominion dig site at the start of the war. The Raiders escaped aboard the battlecruiser Hyperion. The component, and those subsequently retrieved, were stored in the.

Antagonizing the Tal'darim
The Moebius Foundation directed the Raiders to Monlyth and another component. The Tal'darim were already guarding the approaches. This time the zerg, overseen by Kerrigan, arrived slightly before Raiders. With the protoss' attention divided, the terrans again beat the zerg to the component.

A Foundation expedition detected another component inside a xel'naga temple on Xil and moved to excavate it with a Drakken laser drill. They were discovered and wiped out by the Tal'darim. Raynor's Raiders were brought in and they finished the job. The Tal'darim Executor identified the thieves and was most displeased.

The Last Components
Kerrigan determined the Moebius Foundation as the source of the Raiders' success, and attacked their headquarters on Tyrador VIII. The Foundation's public leader, Doctor Emil Narud, summoned the Raiders to destroy the data cores and deny the zerg access to the Foundation's research data. With this done, the Foundation evacuated.

The Foundation quickly set down roots elsewhere and sent the Raiders to Typhon XI. The Tal'darim had not been idle; they established themselves near the component in anticipation of the terrans' arrival. The operation was complicated by the imminent supernova of the local star. The Raiders kept ahead of the planetary firestorm to abscond with the component.

Afterward, the Raiders met with Valerian, and learned of his plans for the device. Despite misgivings amongst his crew, Raynor agreed to join Valerian against the Queen of Blades.

The final component was located on the derelict xel'naga worldship in the Sigma Quadrant. Once again, the Tal'darim were waiting; this time they brought in a mothership to defend the vault. The Raiders destroyed the vault holding the artifact. At last, all the components were brought together.

The Battle of Char
"I just wish the damn thing came with an instruction manual. For all we know we could be upsettin' the entire space-time continuum!" "Easy Tychus, this ain't science fiction."

- Tychus Findlay and Commander Jim Raynor discussing the artifact.

Bringing the device into range of Sarah Kerrigan required the terrans to invade Char. Valerian assembled half the Dominion fleet and placed General Horace Warfield in command. The Raiders joined the battle group. The terrans suffered heavy casualties. Eventually they brought the Keystone to the base of the main zerg hive; the remaining troops dug in around it against the inevitable onslaught. The Queen of Blades personally led the attack; it was an opportunity to acquire the device after having failed to do so earlier in the war. However, the terran defenses held and the fully charged device eliminated the zerg in the immediate area and at least partially de-infested Kerrigan, altering her DNA. Hybrid located nearby collected the energy released from Kerrigan's deinfestation which could be later used to resurrect Amon.

Flashpoint
Afterward, Raynor brought Kerrigan with him onto Valerian Mengsk's Bucephalus, and by fleeing Terran Dominion "justice" they became rebels. Dr. Emil Narud eventually joined them there, where he proclaimed the device a weapon and said that its deinfestation of Kerrigan wasn't an intended function for the device.

Kerrigan and the device were both brought to Space Station Prometheus, a secret Moebius Foundation space station. However, Narud betrayed the rebels to Dominion Emperor Arcturus Mengsk. Raynor and Kerrigan tried to stop him, but he put the device on a warp-capable transport and escaped with it.

Return of the Queen
"Really. Did you think I'd keep an animal like you close to me without some kind of insurance policy?"

- Arcturus Mengsk unleashes the Keystone against Kerrigan in their final confrontation

The device was moved to the Korhal Palace by the time Kerrigan transformed back into a human-zerg hybrid on Zerus. By the time Kerrigan attacked the palace it had been installed as a security device in Emperor Arcturus Mengsk's office; its remote control was disguised as a lighter. When Kerrigan personally confronted Mengsk, he used it to subdue her. Raynor intervened and destroyed the remote before Mengsk could kill her. Kerrigan subsequently killed the emperor.

Legacy of the Void
Guided by Zeratul's advice, Hierarch Artanis and his forces went to Korhal to retrieve the device for the war against Amon. They had to fight through the Moebius Corps forces that had stolen it from the Dominion, while also dealing with the devastating mental pulses that the Keystone unleashed when charged with Void energy. Eventually the Moebius Corps and their hybrid allies were destroyed and the Keystone was recovered.

Phase-smith Karax studied the artifact, and discovered the location of Ulnar, the temple that housed the xel'naga, inside the Alterian Rift where no life should be. When Amon opened a Void rift within the vision temple, the Keystone reacted by absorbing Void energies at an unrepresented rate. Upon further study, Karax discovered the Keystone redistributes essence, matter, consciousness and energy, and that the artifact had been modified from its original purpose. He theorized the artifact would be able to extract Amon from the Khala, thus save the afflicted protoss from his corruption.

On arriving on Slayn, the Keystone again reacted the Void energies on the planet, leading Karax to theorize a connection between terrazine and the void.

Artanis brought the Keystone to Aiur, where it instantly began to react to the presence of Amon by radiating a red glow. Karax expressed concern that though the artifact had been tampered with by Narud to hold the essence of Kerrigan, he did not know for how long it could hold the essence of a xel'naga. Nevertheless, the Keystone was deployed on the surface of Aiur after the destruction of Amon's host body.

Amon sent all of his forces to destroy the Keystone, deploying his zerg, hybrid, and delayed Golden Armada to fight the Daelaam. The combined might of the unified protoss held a defense around the Keystone just long enough for it to gather the energy it needed to pull Amon from the Khala. Executor Selendis engaged Artanis just as the artifact activated, and Artanis convinced her and the remaining Khalai to sever their nerve cords before Amon could break free of the Keystone. One by one they cut their nerve chords, giving Amon no place to go. Amon was forced back into the void, destroying the Keystone in the process.

Wings of Liberty
The Keystone is usable in the final mission of StarCraft II: Wings of Liberty, "All In." It has two charges; one that can be used as a weapon (the energy nova), and the "final blast".

It is capable of unleashing an energy nova that eradicates all hostile zerg within its radius. After the nova is used, the device takes three minutes and thirty seconds to recharge.

Raynor's Raiders must protect it from zerg attacks while the device charges up energy for the final blast; if it is destroyed, the mission ends in failure. Using the energy nova has no effect on the device's charge level. After it fully recharges, it unleashes a devastating blast, destroying all zerg in the area and ending the mission.

Quotations

 * Main article: Artifact quotations

Brothers in Arms
The Keystone is an enemy structure that needs to be destroyed in the mission "Brothers in Arms." It periodically sends out a pulse that disables all terran units and structures.

Salvation
The Keystone is a primary objective in the mission "Salvation". It has to be defended from Amon's forces.

Heroes of the Storm
A xel'naga relic using the model of the Keystone appears in the Machines of War event for Heroes of the Storm, granting bonus gold for players who kill the SCV carrying it. A portrait of the Keystone is available for players who capture a number of these relics.