The Ballistae are large crossbow-like weapons used to annihilate infantry, do decent damage to Swamp Mammoth's, and attack air units. They have very slow speed, and a very long reload time, much like that of the Catapult. They are a very powerful anti-infantry unit as they can do colossal damage to ground units. They are not, however, adept at melee combat, and will quickly die if not supported. It is recommended that you use Ballistae for support only.
Ballistae attack with harpoons that do damage to a narrow but lengthy region. Ballistae can also attack aerial troops and are effective against slow moving large air units.