Hierarchs

The three Hierarchs, also known as High Prophets serve as the highest theocratic leaders of the Covenant High Council. The Hierarchs are exclusively composed of the San 'Shyuum, and use Gravity Thrones decorated with golden backs, equipped with energy shielding and armed with Gravity Cannons. They wear crowns adorned with small holographic projections of Halo. The last three Hierarchs came to power in the beginning of the 9th Age of Reclamation in 2525. The High Prophets are usually replaced all at the same time through political machinations.

Prophet of Restraint
As of 2524, the aging Prophet's tenure had been marked with scandal involving his various sexual exploits, most notably the impregnation of a young female San 'Shyuum while lying about his status and then refusing to abort the offspring. To cover the scandal, he attempted to convince the then Vice Minister of Tranquility to claim the children as his own. The Minister responded by offering to keep the scandal quiet only if Restraint stepped down as one of the leaders of the High Council. The Vice Minister then succeeded him and became the High Prophet of Regret.

Prophet of Tolerance
The Prophet of Tolerance was responsible for the creation of five hundred teams consisting of the most clever and most educated Sangheili and Unggoy to study the human language.

Prophetess of Obligation
One of the most beloved Prophets at the time, she gave birth to triplets in 2524. However, she fell victim to a political shakedown in the Covenant and had to step down from power, replaced by the High Prophets of Truth, Mercy and Regret.

Prophet of Truth


The Prophet of Truth, his former position in the Covenant being the Minister of Fortitude, was the leader of the last three Hierarchs.

Truth offered the former Supreme Commander of the Fleet of Particular Justice the chance to become the Arbiter and ordered him to defeat the Heretics, rebels that regarded Covenant teachings as false, and to retrieve the Sacred Icon on Delta Halo. He spearheaded the purge of the Sangheili Councilors, which sparked the Great Schism.

When Gravemind teleported the Master Chief to High Charity, Truth betrayed Mercy, who was under attack by a Flood Infection Form. He prevented Tartarus from aiding Mercy and escaped to his Forerunner flagship, but not before Master Chief realizes his aim and pursues.

Aboard the Forerunner Dreadnought, Truth then led the Covenant Armada to Earth in order to activate the portal to the Ark. Once there, he set the Forerunner Ship at the base of Mount Kilimanjaro, and began excavating the Ark with Loyalist plasma bursts. Once activated, the excavation triggered a large, stable Slipspace portal to Installation 00. Truth took up residence in the Installation's Control Room in preparation for the Array activation.

Soon after, the Humans and Elites followed through the portal to the Ark. They took down the fortified defenses surrounding the Control Room and deactivated the shield protecting the Citadel just as High Charity exited the portal, spewing Flood forces in every direction. Flood projectiles crippled the Separatist flagship, the Shadow of Intent and prevented the Elite forces from being able to enact the planned mass assault against Truth's final forces. As a result, the Master Chief and Arbiter proceeded into the Control Room, unexpectedly aided by the Flood. The Arbiter then impaled Truth with his Energy Sword, finally putting an end to the deceitful Prophet and the triumvirate of Hierarchs.

Prophet of Mercy


The Prophet of Mercy, whose birth name is Hod Rumnt, originally served as the Philogist on the Forerunner Dreadnought in High Charity. He is much older than any other known Hierarchs.

Mercy served during the trial of the Supreme Commander of the Fleet of Particular Justice, Thel 'Vadamee, and agrees with Truth to promote the disgraced Elite to the rank of Arbiter in a bid for redemption and the eradication of the Heretics.

Mercy, along with Truth, crafted the plans to take the Forerunner Dreadnought to Earth to journey to the Ark, begin the Great Journey, and wipe out the Human Race entirely. Before he could act, however, he was attacked by a Flood Infection Form on High Charity. Seeing this, Truth told Tartarus to "let him be" and then told Mercy, "The Great Journey waits for no one, brother, not even you." The Master Chief found Mercy being consumed by a Flood Infection Form. Mercy then told the Chief of Truth's plans. Master Chief, in return, killed the Infection Form, thus preventing the Prophet from suffering through the assimilation and preventing him from becoming infected. Mercy then collapsed dead from the trauma of being attacked.

Prophet of Regret


The Prophet of Regret, originally the Vice Minister of Tranquility, is the youngest of the High Prophets, and like all Prophets, his name is contrary to his true nature; he is reckless and headstrong, which leads him to commit actions that he should regret, but he doesn't.

After discovering the location of the Portal to the Ark, Regret led the initial, failed attack on Earth with two Assault Carriers and a small contingent of battlecruisers. However, while knowing of the Forerunner structure on Earth, Regret was unaware of Humanity's presence on the planet. After one of the Assault Carriers was destroyed by the Master Chief, he ran through the gauntlet of MAC stations and landed troops in New Mombasa, part of the East African Protectorate, the only place the Covenant landed on Earth. After being repelled by marine forces, he initiated a slipspace jump to Delta Halo.

His actions did not win him a reprieve as Master Chief pursued him through Covenant forces on Delta Halo. Truth, in an apparent attempt to increase his power, called off reinforcement Phantoms, which gave the Master Chief a sufficient window to assassinate him. However, Regret was later revived to a degree by the Gravemind as a Prophet Form and argued with 2401 Penitent Tangent, condemning the ineptitude of the Holy Oracles. He was presumably destroyed when the Master Chief destroyed the Gravemind by firing Halo.

Trivia

 * A recurring theme is that the High Prophets personalities are opposites of their titles (i.e. Truth lies to the Covenant about the Great Journey, the Prophet of Regret never showed regret for his actions, and Mercy showed no mercy to the Arbiter).
 * Each of the three prophets were killed by a different enemy of the Covenant faction. Regret was killed by UNSC, Mercy was killed by the Flood, and Truth was killed by the Covenant Separatists. However, Mercy was the only one not killed by a figurehead, as John-117 killed Regret, Truth was killed by The Arbiter, but Mercy was killed by an Infection Form, not Gravemind, the Flood leader.
 * The High Prophetess of Obligation is currently the only known female hierarch and Prophetess.
 * All of the Prophets in the era of the trilogy were eventually absorbed by Flood.
 * Despite their loyalty to the Prophets, some Covenant members (mostly the Sangheili) do not totally agree about refusing to let Humans join them, some want Humans in the Covenant because they (Humans) are well known and respected for their bravery when seriously outnumbered, unlike Grunts for example, whether the Prophets would use Humans as cannon fodder (due to the war) or respect their intelligence and bravery may not be known.
 * The song 'What I've Done' by Linkin Park has a line which mentions the names of the Hierarchs (Regret, Truth, Mercy). The lyrics go as so: "Cause I've drawn Regret from the Truth... So let Mercy come...". Though this is most likely a coincidence, the members of Linkin Park have stated they are fans of the game. Also, the song's album, Minutes to Midnight, is exactly 1.17 MB large.