Guardian(ガーディアン, Gādian?) is a recurring enemy and boss in the Final Fantasy series since its debut in the original Final Fantasy. It is typically a robotic enemy, though this is not always the case, and is often quite powerful.
Guardian does not appear within the final product of Final Fantasy IV: The Complete Collection. It has a proper name, and was intended to be included in an unused scenario as much of the data still exists in the files for Interlude.
The Guardian is a unique enemy in that it can be fought several times but cannot be killed until the last encounter. As the pinnacle of Magitek machinery, it guards the Imperial Palace in Vector, and later guards the entrance to the city after the Magitek Research Facility is invaded. Kefka brings an escort of Guardians to Thamasa, but dispatches them shortly after arriving. In all of these battles, the Guardian is physically impossible to damage and serves to prevent the player from leaving or entering an area, as it only attacks the party when they attempt to pass it.
The Guardian appears at the summit of Kefka's Tower as the final boss before the Warring Triad. Here it is finally vulnerable to damage and mimics the battle techniques of previous bosses.