"Every member of the Covenant shall walk the path. None will be left behind when our Great Journey begins. That is the Prophets' age-old promise, and it shall be fulfilled!"
The High Prophet of Regret, previously known as the Vice Minister of Tranquility, was the youngest of the three High Prophets that led the Covenant High Council during the Human-Covenant war. Chronologically serving as a secondary villain for Halo Wars and major antagonist for the first half of Halo 2.
He led Covenant forces on the Human Planet, Harvest, assisted by Arbiter Ripa Moramee with the intentions of re-activating a Forerunner fleet. But UNSC forces planned to assault the Apex where Regret was located, so Ripa had him escorted back to High Charity and the Elites was to face Sergeant John Forge and three SPARTAN IIs. Although Ripa and his Elite Honour Guards were killed by them.
Regret led a Covenant Fleet consisted of two Assault Carriers and three Battlecruisers, and went to Earth with the intention of destroying Humanity there. He deployed many Covenant ground forces on Earth and a Scarab in Mombasa, but John 117 and UNSC marines eliminated them. So Regret retreated from Earth aboard his Assault Carrier to Installation 05, who was followed by UNSC Amber In Clad under the command of Miranda Keyes. John 117 and UNSC forces were deployed on the installation and eliminated Covenant forces who were scattered around Forerunner ruins and structures. John soon infiltrated one of the temples where Regret's hologram explained his goals at Installation 05: to fire the Halo Array. John 117 soon eliminated Covenant soldiers in the Forerunner temples and then confronted the Prophet at the main temple where he intended on activating Halo. Regret was heavily guarded by Grunts and Elite Honour Guardsmen, but the SPARTAN managed to kill him by beating the prophet to death. Regret was then captured by the Gravemind and slowly being transformed into a Flood Proto-Gravemind.