On Requiem, the Didact was ready to enact his plans shortly after his awakening; however, the one thing that he still needed was the Composer. As John-117 and Cortana's plan to prevent the Didact from escaping the planet failed due to Cortana's rampancy, his Cryptum flew into the massive Forerunner capital ship, before it emerged from the planet with a score of Liches and a dozen Phantoms accompanying it. Mantle's Approach then entered slipspace to Ivanoff Research Station in orbit over Installation 03.
Despite the efforts of Cortana and John-117, the Didact was able to capture the Composer and test it on the station's crew, composing all humans on board with the exception of John-117. The Mantle's Approach then entered slipspace once more to travel to Earth, but was followed by John and Cortana in a Broadsword. It managed to hold off the UNSC Infinity and Earth's Orbital Defense Platforms for a short time before the Broadsword was able to disable four of its particle cannons. The UNSC Infinity was then able to get close enough to punch a hole in the hull of the Mantle's Approach with its weapons, allowing Chief and Cortana to enter the ship.
Fighting their way through countless Prometheans, Master Chief and Cortana were able to reach the Didact and the Composer, though not before the Forerunner fired the weapon, composing the population of New Phoenix. After a brief confrontation between John-117 and the Didact, John was able to plant a pulse grenade on the Didact's armor, sending him falling into a slipspace fissure underneath the Composer. With time having already run out, John detonated a HAVOK nuke, destroying the Composer and Mantle's Approach while Cortana used the last of her energy to create a hardlight shield in order to protect John-117 from the blast.
The Spartan survived, and the ship was reduced to a cloud of little debris floating in space.
The ship appears to possess no visible means of propulsion. Large sections of the front of the hull open up when the ship jumps into slipspace.
The Mantle's Approach used the Z-330 Independent Actuation Defense Escort/Heavy to help ferry troops around the ship.
- According to Awakening: The Art of Halo 4, the Mantle's Approach is large enough to have a thin atmosphere form on its outer hull.
- Mantle's Approach is the largest ship to appear in the Halo franchise to date.
- Halo: Warfleet – An Illustrated Guide to the Spacecraft of Halo - page 86-87
- Halo 4: The Essential Visual Guide, page 193
- Halo Waypoint - SECTION 3 ARCHIVE
- Halo 4: The Essential Visual Guide - page 204
- Halo 4 - Level: Shutdown
- Halo 4 - Level: Composer
- Halo 4 - Level: Midnight
- Halo 4: The Essential Visual Guide - page 123