Solemn Penance

Regret's carrier was an Assault Carrier that was used by the Covenant Navy in the Battle of Earth, and the Battle of Mombasa. It was commanded by the High Prophet of Regret, making it distinctive from the other ships of its task force.

Battle of Earth
The ship arrived in the Sol System on October 20th as a part of a relatively small task force, composed of itself, another Assault Carrier, and thirteen cruisers, expecting to find and uncover the entrance to the Ark. Instead, they ran straight into the heavy defenses of the UNSC Home Fleet, defending humanity's homeworld. While the cruisers engaged the human warships and orbital defense platforms, the carriers used boarding parties of Elites and Grunts to carry Antimatter Charges into three platforms, intending to blast a hole large enough for them to circumvent the defenses and reach Earth's surface. Though two were successfully destroyed, the second Assault Carrier was destroyed by the Master Chief, using the bomb from Cairo Station. Regret's ship continued unimpeded, descending to New Mombasa, in Kenya, Africa.

Battle of Mombasa
Hovering over the city, the ship deployed massive numbers of ground infantry and heavy equipment, including Scarab walkers, intending to drive the UNSC out of the area and begin its excavations. Unfortunately, they had failed to factor Spartan-117 along with multiple marine regimens and squads into their plans. As a consequence, the Covenant forces were forced to try and fend off a UNSC assault, spearheaded by the SPARTAN Supersoldier. Eventually, faced with the possibility of being overrun on the ground, and intercepted by UNSC ships if it tried to escape to orbit, it activated its slipspace drive in-atmosphere, making an emergency jump - with the UNSC frigate In Amber Clad following it into slipspace. The shockwave from the slipspace rupture severely damaged the city, causing an EMP and partially damaging the city's urban infrastructure AI, the Superintendent. The jump also foiled the attempt of an ODST force to infiltrate the carrier from above, scattering their drop pods around the city and killing most of the troopers.

Battle of Installation 05
The Carrier exited slipspace near a second Halo Installation, and the Carrier again deployed its troops, claiming the Ringworld in the name of the Covenant and transmitting numerous messages from the Prophet of Regret himself to the Prophet of Truth, apologizing for his rash actions. As the UNSC forces, again spearheaded by the Master Chief, closed in on the Prophet, managing to assassinate him, the Carrier used its Energy projector to level the temple where the Prophet had been based, planning to kill the Master Chief. Its attempt was unsuccessful.

The ship's eventual fate is unknown. While it is possible that it was captured by Rtas 'Vadum and his Special Operations Elites and was the Shadow of Intent, this is never explicitly stated. It may even be an unrelated Assault Carrier from the Fleet of Retribution.

List of appearances

 * Halo 2
 * Halo 3: ODST
 * Halo: Ghosts of Onyx