Sublime Transcendence
From Halopedia, the Halo wiki
The Sublime Transcendence was a Covenant Supercarrier, the flagship of the Combined Fleet of Righteous Purpose. It was commanded by Imperial Admiral Xytan 'Jar Wattinree.
In August, 2552 the ship picked up a NOVA bomb along with some mining equipment from Reach, implying that either it was present at The Battle of Reach or visited the planet afterward.
A few months later, during the Civil War of the Covenant, the carrier and its fleet were at Joyous Exultation along with as many other Elite-controlled ships as could be found. They met to plan a strike against the Brutes.
The ship and its fleet, and the planet were all destroyed when Engineers inadvertently triggered the NOVA bomb.