From Halopedia, the Halo wiki
The Lawgiver was caught in the middle of the chaos at the onset of the Great Schism, when Jiralhanae-controlled ships all over the Covenant fleet opened fire on Sangheili vessels. The Lawgiver was held by the Sangheili and when they saw that the Sangheili-controlled cruiser Incorruptible was under attack from the Jiralhanae controlled frigate Twilight Compunction, they subsequently attacked the Jiralhanae ship.
The Lawgiver damaged the Twilight Compunction, but could not destroy it because another ship crossed their field of fire. They also absorbed several plasma torpedoes meant for the Incorruptible, effectively saving the larger ship.
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