Keystone

A keystone is an ancient relic in the Covenant religion. These artifacts were left behind from another time and scattered across the galaxies. The Covenant seek these objects to access a sacred ring, the Halo, through the use of a Blessed One that can activate the keystones.
==History==
===Finding the Madrigal Keystone===
The Covenant attack the planet of Madrigal which triggers the arrival of the UNSC's Spartan super soldiers. After defeating the Covenant, Master Chief examines a cave alongside Kai. They determine that the cave is manmade and that the Covenant are excavating for an object of unknown origin. When he grabs the object, energy ripples through the cave and triggers a sealed memory within Master Chief. He is yanked out of the memory by Kai. The influence of the object continues to affect Master Chief both psychologically and physically. After their ship is shot down, Master Chief touches the artifact once again, receiving more visions, and the artifact emits an energy wave that turns off the power in the UNSC base. It also recharges his ship as the energy courses through the framework.Halo: The Television Series - Season One - Contact
The escaped Covenant Elite relays what he saw to Makee, a Blessed One, explaining that the Spartan activated the object as Makee can. A ring appeared when he touched it, followed by an energy blast. Mercy concludes that it is one of the keystones they have been looking for. Truth wants the keystone, so Makee volunteers to retrieve it. She wants to deliver the gift herself as it will lead them to the sacred ring.
Across the galaxy on the planet Rubble, Master Chief searches for answers about the artifact. Reth, a survivor of a Covenant abduction, examines the artifact. He explains that the Covenant's whole religion is based on objects like this. They are things from another time, things that were left behind. The Covenant roam the galaxy looking for pieces or clues. While Reth was a guest, they asked to see if he could activate them, but he could not, as he's not a Blessed One. A Blessed One is a human, but more so. They have an obligation, a responsibility, a moral imperative. John activates the object and it sends out a blue energy wave that fills the entire refuge. A symbol appears on the artifact and a ring of symbols around it. As the electricity crackles, John is mesmerized by the artifact and experiences memories of his childhood once more. He returns the artifact to the box when the visions pass. Reth questions who John is as he can bring it to life but is different than the one the Covenant has. He realizes that John doesn't know what he is, saying it's in his eyes. Reth explains that the ring John made appear is what the Covenant wants. It's a door to the end of life as they know it, a weapon. Reth asks John if he felt the darkness and he did. That means John can stop it by destroying the artifact and then himself. John ultimately chooses to return to Reach as he needs the help of his fellow Spartans.Halo: The Television Series - Season One - Unbound 
Meanwhile, Halsey runs more tests on John with help from Adun and Cortana, with John unlocking more memories. This intensifies after he removes his hormone pellet. He remembers drawing the object as a child and then burying it in the forest with his father, and an image of the Madrigal object fitting into a larger object. He believes the larger object is buried in the woods of his home world Eridanus II. He recruits the Spartans to help him locate it, with Halsey joining the mission. Across the galaxy, Makee begins her search for the keystone and murders members of a UNSC ship to obtain information, ultimately deciding to continue her mission on Madrigal and track the keystone from there.Halo: The Television Series - Season One - Emergence
Dr. Miranda Keyes runs her own tests on the object, confirming that none of the other Spartans can activate it. Miranda and the Spartan Kai review a distress call sent from the hijacked UNSC ship, as Kai can understand portions of the Covenant language. Kai translates one of the words as "keystone", another as "sacred ring", and recalls the ring that appears around the Madrigal keystone when activated. She and Miranda realize that the sacred ring is the ring projected from the Madrigal artifact.Halo: The Television Series - Season One - Homecoming
===Finding the Eridanus II Keystone===
After removing his hormone pellet, John made contact with the Madrigal keystone once more, as he correctly believed the pellet limited what he was seeing in the visions. As childhood memories resurfaced, he saw himself as a young child roaming a planet and sketching ferociously. He happily showed his mother how the smaller artifact fit into the larger one. He broke the connection to the Madrigal keystone and informed Halsey of his belief of a second, larger object located on his home planet of Eridanus II. His father had forced him to bury the sketches, and possibly the object, both of which he hoped were still there. While the excavation only revealed his childhood sketches, being back on his home planet helped John to remember more of his childhood, including when he activated the larger keystone as a child. He guided Halsey and Adun to a cave just beyond the Reach For Life borders, and discovered the massive keystone encased in a boulder.
The UNSC rallied to excavate the object, which was not only encased in a boulder, but sealed behind a crystal substrate. Miranda noted the substrate was too clear to be naturally occurring. Halsey ignored her and when Adun used a laser to shatter the substrate, it emitted a blast of sonic sound waves that debilitated every being in the vicinity. The blast also shattered the crane. On Madrigal, Makee touched the location of the smaller keystone and was struck with a vision of the larger keystone. Master Chief remained unaffected by the sound. Once the substrate finished shattering, the sound ended, but everyone's ears bled.
Miranda identified the noise as a signal, whether to keep them away or to communicate with something. She thinks they objects aren't two halves of the same weapon, but another device altogether. Master Chief later touched the artifact and received more memories of his childhood, though the effects were much harder on his body and could have killed him. When The Covenant attacked, the Spartans were ordered to manually deliver the keystone to Miranda's ship. In the process, Master Chief abandoned his team to save Kai's life. The Spartans vehicle crashed and the Covenant stole the artifact.Halo: The Television Series - Season One - Reckoning
===Battle on High Charity===
Makee stole the UNSC's keystone and brought it to High Charity to begin the ancient ritual to unlock the star map. Silver Team arrived to steal the keystone back to avoid the Great Journey, which would eliminate all human life and allow the Covenant to travel to the Halo alone. During the battle, Makee made contact with the now-assembled keystones to save John. The blast knocked the Covenant to the ground and they proceed to kneel to watch the event unfold. A constellation began to project above the temple. Makee and John were rendered unconscious and taken to the Halo. Kai killed Makee to free John from the Halo, though he was faced with a choice between the Spartans and the artifact. He ultimately let Cortana take control and she expertly killed hundreds of Shangheili forces, saved the Spartans, and procured the artifact without activating it.Halo: The Television Series - Season One - Reckoning 
==Known Keystones==
*Madrigal Keystone - The Madrigal keystone is one of the keystones from the Covenant religion, and was excavated from the planet of Madrigal. Initially uncovered by the Covenant, it was ultimately taken by the Spartan Master Chief. He activated the artifact inadvertently, and once used the power to energize his ship. It also breaks down the programming implemented by Dr. Halsey that makes Master Chief compliant with the UNSC's orders. Master Chief is the only known person who can activate the Madrigal keystone, as it did not react to Soren or Reth's contact. The object unlocks memories of his childhood, including his drawings of the object and a larger piece that the Madrigal keystone fits into. Admiral Parangosky confirmed that the object was over 100,000 years old, meaning its pre-human and possible pre-Covenant. It's organic with an inherent technology. With the possibility of it being part of a weapon, Admiral Parangosky assigned Dr. Miranda Keyes a parallel team that would analyze the object. Meanwhile, the object unlocked more memories that John had, especially after he removed his hormone pellet. The artifact was later stolen by Makee and combined with its larger counterpart. The assembled piece was taken by the Spartans.
* Eridanus II keystone - The second, larger artifact, was found on Eridanus II in a cave just outside the Reach For Life Installment. As a child, John sketched it repeatedly in an obsessive nature before he found and activated the keystone himself. His parents forced him to bury the sketches, and the Spartan programming he endured erased his memory of the object. He returned decades later and found the keystone once again, but this time, shared the discovery with Dr. Halsey and Adun. As the UNSC attempted to excavate the object from is enclosure, they ruptured the substrate around it, which alerted the Covenant Blessed One to its location. The Covenant attacked and stole the artifact from the UNSC before escaping into slipspace. It was ultimately reunited with its smaller counterpart by Makee. The now-assembled keystone was taken by the Silver Team of Spartans on behalf of humanity.
==Trivia==
* The Shangheili word for keystone is "Oq'ogakha" and the term used to describe the sacred ring, otherwise known as Halo, being "Ch'anggagomo".
==Appearances==
* Halo: The Television Series - Season One
** Contact (Madrigal Keystone only)
** Unbound (Madrigal Keystone only)
** Emergence (Madrigal Keystone only)
** Homecoming
** Reckoning
** Solace (Madrigal Keystone only)
** Allegiance (Madrigal Keystone only)
** Transcendence
==Gallery==
Halo_101_The_Artifact.jpg
Halo S1 First-Look4.jpg
Halo_104_Keystone.png
Halo_104_Keystone2.png
Halo_104_John-Activates-Keystone.png|Young John activates the keystone
Halo_104_Keystone-Sketch.png|John's childhood sketches
Halo 109 Makee-Keystone-Still.jpg|Makee activates the assembled keystone
==Sources==
Category:Halo TV show