The Guardians were a group of Cylon-War era Centurions that piloted a single basestar, containing the first Cylon Hybrid, into deep space following the Armistice. Utilizing decades old Raiders and weaponry, the Guardians operated entirely separately from the rest of the Cylon civilization, becoming something of a Cylon legend.
These Centurions guarded the original Hybrid, still alive over 40 years after its creation. Seeking to further their evolution and continue the experiments begun during the first Cylon War, the Guardians captured a civilian science team from the surviving Fleet following the Fall of the Twelve Colonies. This triggered a battle between the Guardian baseship and the Battlestar Pegasus, under the command of Lee Adama. During the battle, an assault team lead by Major Kendra Shaw boarded the basestar and rescued the science team, detonating a nuclear weapon that destroyed the ship and killed the Hybrid ("Razor").