From Halopedia, the Halo wiki
The Reformists, also known as the Reformers, were a faction of San'Shyuum who opposed the Stoics, wishing to infiltrate and study the Forerunner Dreadnought in order to advance their species and better understand their gods. These differences ultimately culminated in the War of Wills, which saw the Reformists flee Janjur Qom aboard the Dreadnought.
The San'Shyuum homeworld of Janjur Qom was populated with many powerful Forerunner relics, leading the native population to form a religion around the makers of these artifacts. The San'Shyuum believed that the Forerunners had achieved divinity via the activation of Halo, which they called the Sacred Rings. However, these beliefs were based on fundamental mistranslations of artifacts, skewing the San'Shyuum's decisions for millennia to come. By far the most influential of all the Forerunner relics on Janjur Qom was the Anodyne Spirit, a keyship which had crash-landed in the Great Apothtea sea.
Referred to as the "Dreadnought" by the San'Shyuum, this majestic vessel would become the driving factor in the species' fragmentation. Some San'Shyuum—the Reformists—thought that they should enter the keyship and explore its interior to better understand their gods, believing that their artifacts had be left behind specifically for them to activate, explore, and even dismantle, if necessary. Yet, many San'Shyuum—called the Stoics—believed that Forerunner artifacts should only be deferentially observed, and that entering the Dreadnought would be tantamount to the desecration of a holy site. While the debate started out entirely political and philosophical, it devolved into violence as more and more San'Shyuum left the Stoics to join the Reformists, leading the Stoic leaders to suppress their opposition via imprisonment and execution.
War of Wills
The violence came to a head in 2200 BCE and ignited a long, bloody conflict known as the War of Wills. During the civil war, the Reformists established a stronghold in the fortress of Granduin in the Zelfiss region. However, the fortress was undermined by Stoic forces, causing it to fall into the nearby Great Apothtea sea. During the climax of the San'Shyuum civil war, around one thousand Reformists stormed the Dreadnought and began to occupy it, while preparing to use the vessel to leave Janjur Qom. The Reformists occasionally raided Stoic territory to collect and stock the ship with plants, wood, seeds, and other goods from the planet.
At the end of the century-long conflict, one thousand heavily-armed Reformists infiltrated the Dreadnought, barricading themselves inside. The Stoics' unwillingness to damage the holy artifact resulted in a protracted standoff. To the Stoics' immense surprise, the Reformists eventually managed to ignite the Dreadnought's engines and escape Janjur Qom, blasting a huge chunk out of the planet in the process. Refusing to fire on the vessel, the Stoics grudgingly allowed the Reformists to leave. While Reformists ultimately won the conflict, it came with a heavy price; they were left with only around one thousand individuals, and were forced to selectively mate to prevent inbreeding. The Roll of Celibates was established in an effort to maintain genetic diversity between the San'Shyuum and to eliminate unwanted genes.
Soon after fleeing Janjur Qom, the Reformists used the Dreadnought to investigate orbital installations around Salosur Qom, a neighboring world in their home system of Qom Yaekesh. Within these facilities, the Reformists discovered provisions, intriguing artificial creatures known as Huragok, and a powerful Cartographer. When this machine fed information into the Dreadnought's own systems, it activated a device called a Luminary, a system that could guide the Reformists to other worlds stocked with Forerunner relics. Gathering many of the Huragok onto the Dreadnought, the Reformists then followed the Luminary's signal away from their star system and into the vast galaxy.
For hundreds of years, the Reformists wandered across the stars aboard their Dreadnought, discovering vast Forerunner reliquaries on abandoned worlds and in derelict installations. As time went on, the Huragok helped the San'Shyuum unlock many secrets pertaining to the Forerunners, further crystalizing their belief in them as gods.
War of Beginnings
In 938 BCE, the Reformists came across Ulgethon, a world that they thought was entirely uninhabited. However, as they investigated repository of Forerunner relics, they discovered an intelligent species living among the artifacts. Known as the Sangheili, this species similarly worshipped the Forerunners, but they believed that any direct manipulation of their gods' technology was tantamount to blasphemy and punishable by death. When the Sangheili discovered the Reformists' plan to excavate Ulgethon's artifacts, Arbiter Vema 'Togad slaughtered and decapitated a San'Shyuum delegation, sending their remains back to the Dreadnought as a warning. Horrified and outraged, the Reformists fled into space, where their Dreadnought was confronted by a Sangheili blockade. The ensuing ground and space battle resulted in the razing of Ulgethon and its population, and served as the first engagement of the decades-long conflict that would come to be known as the War of Beginnings.
The war would spread across many Sangheili colonies as the San'Shyuum sought to obliterate the Sangheili at the behest of their leader, Pervading Stone, who was also the head of the Keepers of the Dawn. His father had fallen to the Sangheili during the battle at Ulgethon, driving Stone's need for revenge. Even though the Reformists' Dreadnought seemed unbeatable, the Sangheili fought back, and even managed to ambush and board the vessel at their colony of Codisfold, killing thousands of San'Shyuum in the process. While the boarders were eliminated, this event began to shift the hearts of many Reformists as they realized that they were not as untouchable as they previously believed. Some members of the Keepers of the Dawn—Breaking Shadow and Ushering Dusk—even spoke out against Pervading Stone, who responded by secretly having Ushering Dusk assassinated. Still, this did not remove the seeds of the doubt that were sown in the minds of the Reformists, and many would begin to consider the possibility of peace with the Sangheili after they were forced to amend the very beliefs that had sparked the war and use their own Forerunner weapons against the San'Shyuum in an act of desperation. Despite this, Stone continued his campaign against the Sangheili, eventually bringing the Dreadnought to their homeworld of Sanghelios in a fateful final battle. For a time, Sanghelios and its two moons were embroiled in conflict, ravaging their surfaces. This continued until the Sangheili unleased the Reckless Pursuit, a R'sikosh-pattern man o' war fitted with powerful Forerunner-derived weaponry, and shot down the Dreadnought on Suban.
Before the Reformists could recover and flee, the Dreadnought was held in place with gravity anchors, trapping them. While the Sangheili discussed what their next move would be, tensions amidst the San'Shyuum came to a head. By 855 BCE, Breaking Shadow led a coup against Pervading Stone, killing him and effectively becoming the new leader of the Reformists.
Formation of the Covenant
In 852 BCE, while the Reformists were still trapped on Suban, Breaking Shadow and an unarmed delegation met with the Sangheili, represented by First Kaidon Pelahsar the Strident. During this meeting they forged a tenuous truce, forgiving each other for their past crimes and working toward peace as they had come to realize that extinction was a possible outcome of continued conflict. Soon after this, the truce was ratified with the Writ of Union, a document of covenant between the two species and official recognition of their sole focus of worshipping the Forerunner through the discovery and exploration of their artifacts. This would mark the birth of the Covenant, an empire founded on the belief that the San'Shyuum and Sangheili could work together to pursue transcendence via the activation of the Sacred Rings.
List of appearances