From Halopedia, the Halo wiki
The carrier was present during the Covenant's invasion of the Epsilon Eridani system in the summer of 2552. During the series of battles that occurred throughout the system, Splendid Intention carried plans for new Sangheili weapons that were allegedly powerful enough to render the Covenant's contemporary energy projectors obsolete. During the battles in the system, Splendid Intention attempted to transfer the plans to other frontlines in the war.
When the United Nations Space Command became aware of these plans, a team of Spartan-IIs was dispatched from UNSC Of Uncommon Courage and tasked with infiltrating Splendid Intention to steal the plans and deliver them to the UNSC. During the raid, a series of events occurred which are classified by the UNSC, though it is known that the mission did not go as planned. Ultimately, Of Uncommon Courage was sacrificed to ensure that Splendid Intention was downed in the southern waters of the Cortez Ocean on Beta Gabriel, a human colony in the Epsilon Eridani system.
After the war, the Office of Naval Intelligence established Fathom Station along the Aleutian Rim near Splendid Intention's crash site, with the intent to search for the weapon plans aboard the carrier. However, in 2556, while a team of explorers was searching the carrier, Splendid Intention suddenly shifted from its resting place along the rim and slid down a trench, sending debris and water into Fathom Station's northern terminal. The debris destroyed the station, killing everyone aboard.