These robots are operated by the [Divine Messenger] that aids the Sacred Army. Their strength far surpasses the Army's knights, and there are quite a few of them, too. Problematic opponents.
These monsters are robots that were created as Guardians for the Second Tower of Ar tonelico, all of which are under the direct control of the Goddess and her subordinates. Given this, they are very strong, and they are fought during several points in the game's story.
The only significant difference between each encounter is the stats, as all versions of the Divine Armies share the same moveset and status resistances. Their attacks are Gyro Screw, in which they spin their arms around to create a tornado that hits a party member four times, Megaton Combo, which is a one-two punch that hits twice, and Rocket Dive, which only hits once. Gyro Screw and Megaton Combo are a bit tricky to block perfectly, but as long as the player is careful, they shouldn't have many problems reducing these robots to bits of scrap. Likewise, while most times these enemies come alone, they also show up every now and then as companions to some bosses, so in these ocassions, it would be advisable to dispatch the Divine Armies first to be able to concentrate better on the boss itself.