From Halopedia, the Halo wiki
The Kewu-pattern is a ship seemingly purpose-built for the task of destroying other Covenant warships. The vessel masses out at 500 million tonnes, over three times that of a typical Covenant cruiser. and sizes up at three times the size of a typical UNSC cruiser; laying at 3.5 kilometres in length.
The ship is capable of withstanding three Magnetic Accelerator Cannon rounds and hundreds of M58 Archer missiles before losing its shields, as well as surviving a dozen Archers to its unshielded hull with minor damage.
The Kewu-pattern was comissioned, unusually, by the Ministry of Concert during the Ninth Age of Reclamation. This was viewed as highly unusual, and the design broke many conventions of naval architecture and pattern approval processes, though was ultimately blessed by the Hierarchs in an extremely unorthodox process. The Ministry of Concert's charge of ensuring the governance and subjugation of lower-caste species in the empire may be the primary reason for the ship's overwhelming focus on countering other Covenant vessels.
Fall of Reach
The only such vessel known to have been encountered by the UNSC was present at the Fall of Reach on August 30, 2552, where it served as a secondary flagship for the Fleet of Particular Justice. During the battle, it remained outside the range of the planet's orbital defense platforms and destroyed many UNSC ships, including the Musashi, the Minotaur and the Herodotus. Soon, the UNSC Pillar of Autumn used three shots from its upgraded MAC and over 500 Archer missiles to drop the ship's shields and apply minimal damage to the hull. The Pillar of Autumn then launched a remote-controlled GA-TL1 Longsword armed with a Shiva-class nuclear missile, which impacted the ship while its energy shields were recharging. The explosion was contained by the newly regenerated shields, multiplying the destructive blast exponentially, and the ship was destroyed.
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