Deadbolt

"A deadbolt needs a key—it is not the key. It is put in place to keep something locked safely away."

- Walking-in-Light-of-Falling-Stars explains the purpose of a deadbolt.

A deadbolt is a form of Forerunner technology designed to keep something locked safely away. Engineers were familiar with deadbolts.

History
"The Deadbolt, they called it, though perhaps 'they' had no idea, really."

- Splendid Dust, while discussing the construction of the Mysterium and the deadbolt there.

A deadbolt, known properly as the Deadbolt, was ostensibly used to secure a wealth of Precursor technology in Maethrillian's Mysterium during the Capital's construction. The entire megastructure was built around the Mysterium and the Deadbolt. This deadbolt was not a security measure for the Mysterium, however. It was in fact what secured access to the Domain itself. The Ecumene Council's First Councilor was entrusted with the key to the Deadbolt, which was hidden among the formal collar that adorned their regalia alongside other keys.

Well over a century after the Halos' activation, a number of Forerunners returned to Maethrillian on a mission to repair the Domain, which had been rendered inactive by the Halos. As former First Councilor, Splendid-Dust-of-Ancient-Suns possessed knowledge of a Precursor relic—the Organon, housed deep within the Mysterium, believed to control the Domain itself—and the Deadbolt key to activate and interact with it. Upon arrival, the Organon revealed itself to be a powerful construct called Abaddon which desired to bring the Forerunners to trial for their crimes. Abaddon killed two of the Forerunners but it vanished when Growth-Through-Trial-of-Change used the key to successfully begin the process of restoring the Domain. In doing so, she vanished in a flash and was presumed deceased.

Description
The specific deadbolt key that could interface with Abaddon and the Domain was hexagonal in shape. Bornstellar-Makes-Eternal-Lasting thought it pretty and radiant and noted that it looked as though it had been newly-created from hardlight, even though it was in reality precisely carved from stone. It typically hung from the First Councilor's collar, hidden in plain sight. The Mysterium's deadbolt itself took the form of a slag heap wherein one stone was a deep, beautiful, amethyst hue. Feeble light sparked along its edges and outlined a hexagonal hole for the key. The Deadbolt could be glamoured to keep it from sight, instead replaced by the imposing avatar of the Precursor creation, Abaddon.

List of appearances

 * Halo: Cryptum
 * Halo: Fractures
 * Promises to Keep