Keystone

"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 Jim Raynor discussing the artifact.

The Keystone was one of the major catalysts of the Second Great War. Its effects were harmful to the zerg.

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 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 have not had such experiences.

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

The Keystone was considered a weapon by 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 deinfest an infested terran (Sarah Kerrigan) was not the way the designer intended the device to be used.

The Keystone is unique in xeno-archeological terms in that by the early 26th century, the first piece (recovered from Mar Sara) was determined 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.

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 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
After the Great War, the terrans, protoss, and zerg took an interest in the device.

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 device. 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.

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 Jim Raynor and 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 the Moebius Foundation's true leader, Prince Valerian Mengsk, and learned of his plans for the device. Despite misgivings amongst his crew, Raynor agreed to join Mengsk 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
Bringing the device into range of Infested Kerrigan required the terrans to invade Char. Prince Mengsk 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 device 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.

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 device 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 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, Artanis and the remnants of the Golden Armada 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.

Game Effect
The artifact 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".

The artifact 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. 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