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Only a third the size of the UNSC Commonwealth, the ship appeared to be crewed exclusively by Kig-Yar. During the Spartans' exploration of the ship, no personnel of other species - Sangheili, for instance - were called in to halt the alien attack. This indicates the ship may have been an artifact-retrieval vessel sent out by the Ministry of Tranquility to search for holy relics. Despite its small size, the ship was capable of enduring significant amounts of punishment from the UNSC Commonwealth and nearly bested the human ship in combat.
As the UNSC Commonwealth approached the Damascus Materials Testing Facility on Chi Ceti IV, the Unrelenting launched an attack on the UNSC frigate and was able to severely damage her with pulse lasers and plasma cannons. The Commonwealth retaliated with Archer missiles, which proved ineffective, and a single MAC slug, which temporarily knocked out the vessel's shields and dealt enough damage to the Unrelenting for Spartans to be able to board it. During combat it was boarded by three Spartan-IIs, John-117, Kelly-087 and Samuel-034, all of whom had infiltrated the ship by slipping into a hole the Commonwealth's MAC had created.
The Unrelenting was destroyed when the three Spartans fought their way to the ship's reactor and placed Anvil-II air-to-surface missiles nearby, detonating them when the Spartans were clear of the ship. Unfortunately, Samuel's Mjolnir suit had been breached when it was damaged during a firefight, and he was unable to evacuate the ship. He instead stayed aboard and activated the missiles.
The Spartans captured a Kig-Yar energy gauntlet at one point while on the ship. The crew of the Unrelenting was later accused of having a "lack of faith" by the Prophet of Regret for failing to repel the Spartan soldiers and destroy the human ship.
By March of 2526, the Covenant remained unaware of exactly what had befallen the Unrelenting. A dispatch sent to the Fleet of Inexorable Obedience during a lull in the battle expressed the confidence of the Shipmaster that after a fierce initial engagement, the vessel would prove victorious and then seek repairs at Zhoist. However, the Unrelenting never arrived and its fate was the subject of much speculation amongst Fleetmaster Nizat 'Kvarosee's staff officers. As a result, when the United Rebel Front offered information on the destruction of the Unrelenting alongside that of the Radiant Arrow, Nizat's interest was drawn.
In the Halo: Fall of Reach comic adaptation and Halo: The Fall of Reach - The Animated Series, Unrelenting is depicted as a CCS-class battlecruiser. This is a departure from the novel, which describes the ship as being a sleek ovoid a third the size of the Commonwealth, with a single lateral line running its length. Frank O'Connor commented that Covenant ships in the animated series were portrayed differently from the novel for the purposes of the adaptation, leaving the ship's canonical class ambiguous. In Halo: Silent Storm, Vice Admiral Michael Stanforth stated that the Unrelenting was "frigate-size," but did not go so far as to actually call it a Covenant frigate.
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