The Guardian of the Night (FR-22K) is a Charon-Class Light Frigate (the same class as the Forward Unto Dawn) primarily used by members of the Order of the Just that are stationed to serve Princess Luna. It was put into service after the end of the war against the Extremist Coalition of the Fire Nation.
Its service number, FR-22K, is a reference to the Fire Rebellion Storyline and LOTM user 22kingdomheartsfan.
In Season 15, it was damaged after it engaged in a tactical collision with the Warrior Dome, killing nearly 50 onboard, including Order of the Just Lieutenant General Briggs. After Briggs' death, Tempest Shadow was appointed as the ship's new Captain. It was later repaired, turning it into the Guardian of the Night Mark II.