Prophet of Regret

I shall light this holy ring, release its cleansing flame, and burn a path into
the divine beyond!"
—Prophet of Regret

The High Prophet of Regret is the youngest of the three High Prophets that lead the Covenant High Council.

Biography
Twenty Third Age of Doubt
During the Age of Doubt, 2524 by the UNSC calender, the Prophet of Regret was known as the Vice Minister of Tranquility. He was unique amongst his Prophet fellows in his confrontational attitude and combative demeanor, a trait he had gained from spending a good deal of time working with Elites. He was the first to inform the future Prophet of Truth about the existence of Harvest and what they believed to be a vast reliquary of Forerunner artifacts (In reality, these "artifacts" were nothing less than the humans on the planet, or "Reclaimers"). After persuading the future High Prophet to join him in a conspiracy to gain these artifacts for their own private usage, he helped Truth in his plans by pretending to sympathize for those blacklisted from reproducing due to inborn genes, which included the then Hierarch Prophet of Restraint. After pretending to be the father of an unlawful child the Prophet of Restraint had fathered, Regret forced Restraint out of power by threatening to reveal the scandal if he did not leave his position as High Prophet.
Before their coup, the Prophets visited an "Oracle" within the Forerunner Dreadnought, an ancient AI known as Mendicant Bias that had stored itself in the ship and had not spoken to anyone for several hundred years. When the Luminations of Harvest were entered into its matrix, it suddenly came to light and revealed the symbols had been misinterpreted-that humans stood as equals to the Forerunner, and the Covenant had been mistaken in their beliefs. As it tried to launch the Dreadnought from High Charity, the Prophets along with the Philologist, leader of the ascetic priests and later the Prophet of Mercy, disconnected the Oracle from the ship and decided that the humans must be eradicated once and for all, before any of the Covenant could learn of this and shatter their entire existence.
He served during the destruction of Halo Installation 04 and was one of those who publicly condemned the Sangheili Commander who was responsible for the loss of the ring. While he appeared for the trial, it was by way of hologram, as Regret was en route to Earth, searching for a method to initiate the Great Journey.

On the Path to the Great Journey
Earth
"The message just repeats, "Regret, Regret, Regret.""
—Cortana
Despite being chided by his two compatriots, The Prophet of Regret led the first attack on Earth. His fleet was small for an assault, totaling only two Assault Carriers and thirteen CCS-class Battlecruisers. It is thought that he was directed to Earth by a Forerunner artifact, perhaps the one on Coral to search for the Ark, but he apparently had no knowledge of a human presence on Earth and that it was his enemy's home world. Nevertheless, he sent Ranger Elites and Boarding Craft to destroy the Orbital Defense Platforms Malta, Athens, and Cairo, so he could push through into the heart of Africa. Despite the Master Chief's actions, his ship made it to the ground and deployed the first full-scale invasion force of Covenant on Earth.
After landing in New Mombasa to search for the Forerunner artifact located on Earth, Regrets forces deployed numerous ground units to further search the city, including at least two Scarabs and many Phantom dropships. As Spartan-117 approached his Carrier, Regret's ship initiated a Slipspace jump right in the middle of New Mombasa to escape his pursuers and regroup his attack force. The move was so surprising that only the UNSC In Amber Clad and four Prowlers were able to follow the Carrier as it jumped and destroyed the city.

Delta Halo
"I shall light this holy ring, release its cleansing flame, and burn a path into the divine beyond!"
—Prophet of Regret
Regrets Carrier landed ground and infantry forces onto the surface of Installation 05, and the Covenant, under Regret's say so set up a presence around a "temple" in the middle of a lake, from which Regret began his religious sermons. He also transmitted an apology to the Prophet of Truth, indicating that he couldn't have known that the humans would be there or in such force. Truth responded by saying that only Mercy had spared him from "public" condemnation. Nevertheless, High Charity and the Second Fleet of Homogeneous Clarity rushed to the new Halo, and a flight of Phantoms was deployed to rescue the Hierarch.
The In Amber Clad arrived in system soon after and deployed ODST forces onto the surface of Installation 05 along with the Master Chief to locate and kill Regret. The operation was a success, but soon afterward High Charity made a jump to the ring and ordered one of the nearby ships to use its Gravity Lift to destroy the temple, nearly killing the Spartan and negating any chance of rescue for the Prophet.

It isn't known how Regrets body escaped the destruction of the temple, but it was later assimilated by the newly formed Gravemind, reanimated and incorporated into the creature itself. He made a final appearance at the beginning of the next level, where he expressed annoyance with another captive of the Gravemind's, 2401 Penitent Tangent, and reacted to the presence of the Arbiter, warning the Arbiter to forgo any heretical suggestions made by the Monitors and the humans and to pursue the Great Journey.

The Ark
Throughout the events of Halo 3, Regret likely remained a part of Gravemind. If this is true, then Regret was finished for good on the Ark, where the Gravemind was killed due to the activation of the replacement of Installation 04.

Personality
Based on a letter written from Truth to Mercy relating to his untimely attack of Earth without realizing the significant human presence and defensive measures, Regret is considered a very rash and ambitious Prophet, immature and naive compared to the other ladder members. He developed a habit of ingesting excess alcoholic beverages, and his work as Vice Minister of Tranquility meant that his duties brought him into regular contact with the Sangheili, and had adopted some of their personal traits, such as a preoccupation with honor and personal arms. During their visit to the Oracle upon the Forerunner Dreadnought, Regret, then still a Vice Minister, first tried to threaten a Lekgolo pair with a Plasma Pistol and then almost shot the Philologist, later to become Mercy, for "tampering" with the Oracle.

Combat
The only weapon Regret has is his Gravity Throne. It is only seen being used as a weapon in Regret. Regret's gravity throne is equipped with two Gravity Cannons that glow bright red and are a modified version of a Hunters Fuel rod gun. It is also equipped with a teleportation device that allows him to teleport a short distance away. The only way to defeat him is to board his throne and melee attack him. However, rockets will lock onto the throne as if it were a vehicle. Though this will not kill the Prophet, enough rockets can hurt him, reducing the number of hits he can take once you board his throne. Also a lunge with the energy sword will weaken him, though not as much as a rocket.
After a few hits, he will throw you off and teleport away, and his throne must be re-boarded to resume the assault. This pattern will repeat until either he or the Master Chief dies.
Regret is not alone, however. Throughout the battle with him, Grunts and Honor Guard Elites will attempt to aid him against the Chief.
Due to a glitch, Regret can be knocked out of his throne and shoot you with a plasma pistol that has a faster rate of fire for a few seconds. Regret will then teleport back to his chair as if nothing had happened.