You'll run into Guard Beasts while you're being pursued by Kakanas on the White Boa. You'll also face them if, while you are in battle with a Security Eye, the eye uses its Alarm Lv 2 ability. Guard Beasts are pretty basic enemies. A spell cast should take them down, if not one spell and a physical attack. Their main function is just to serve as a shield for the security eyes. However, if they are in battle with a Numara Soldier, the soldier and the beast may do a combo attack called "order," a physical attack that does decent damage.