Prophet of Regret
From Halopedia, the Halo wiki
Summary
The Prophet of Regret is one of three High Prophets that lead the Covenant High Council.
Regret was never mentioned until his appearance in Halo 2. He led the first attack on Earth. His fleet was small for an assault, totaling only two Assault Carriers and thirteen CCS-class Battle Cruisers. It is thought that he was directed to Earth by a Forerunner artifact, perhaps the one on Coral, for he apparently had no knowledge of a human presence. Nevertheless, he sent Rangers and Boarding Craft to destroy the orbital super MAC guns and then directed his two carriers to punch through the UNSC Defenses. Only the one he was on made it through, thanks to the quick actions of the Master Chief.
He landed troops in New Mombasa, the only place the Covenant land on Earth. The attack on the city was a disaster, the confused Covenant were not prepared to fight such a massive human stronghold. Regret released at least one Scarab into Old Mombasa, indicating that he was digging for something.
Regret's carrier suddenly initiated a slipspace jump right in the middle of New Mombasa. It is suspected that he had found the location of Installation 05 on Earth, because his lone carrier jumped streight to the Halo. The move was so surprising that only the UNSC In Amber Clad was able to follow the Carrier as it jumped and destroyed the city.
His Carrier landed forces on Installation 05, and the Covenant set up a presence around a Temple in the middle of a lake, where Regret began issuing sermons, perhaps in preparation to try to activate the Halo. He also transmitted an apology to Truth, apologizing for his reckless attack on Earth. Truth responded angrily, saying that it was only Regret who had stopped Truth from publicly condeming Regret. Nevertheless, High Charity and its fleet rushed to Installation 05 and released a fleet of Phantom dropships full of forces to save Regret from the humans who had overwhelmed Regret's own army.
His sermons were interrupted when the Chief bursted in, and managed to attack and kill him. The rescue Phantoms were called back by Truth, and instead a Covenant cruiser quickly destroyed the temple with an energy beam.
Regret's body apparently survived the destruction of the temple, and it floated into the lake where it was picked up by the Gravemind. Gravemind then reanimated Regret, turing him into a "Prophet form" of the Flood.
He made a final appearance in the grasp of Gravemind, where he argued with 2401 Penitent Tangent about the existence of the Great Journey. It seemes that Regret was conscious and retained his personality, contrary to the mindless, silent Combat Forms, suggesting that Regret was not actually infected by the Flood, and perhaps that he even survived the Master Chief's attack.
Combat
Regret floats around in a gravity-throne equipped with a weapon reminiscent of the Hunters'(called a Gravity Cannon in Halo 2's files) that fires golden blasts of energy, and is impervious to direct attack. 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 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.
After a few melee 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 falls.
Regret is not alone, however. Throughout the battle with him, Grunts and Honor Guard Elites will attempt to aid him against the Chief.
Combat Quotes
"This, is the humans greatest warrior?"
"Warriors, attack! The Demon must die!"
"Your very existence offends me, Demon!"
"Guards! Remove this vermin from my sight!"
"You dare to interupt my sermon!?"
"Incompetents! I'll kill him myself!"
"The Great Journey will not be postponed!"
"Surely, you can do better than that!"
"Perhaps you have underestimated me, no?"
"Why anyone would fear this Demon, is beyond me!"
"Human filth! You emboule this holy place!"
"This, is the humans' greatest warrior? Ha ha ha!"