The rock-paper-scissors model governs most units in battle. For example, infantry do additional damage to cavalry, cavalry do additional damage to archers, and archers do additional damage to infantry. The same rock-paper-scissors formation exists in the three different types of naval units—arrow ships, siege ships, and hammer ships. Siege units are generally exempt from the rock-paper-scissors model but are instead able to destroy buildings easily while being vulnerable to cavalry attacks. Heroes are extremely effective against myth units, which in turn do large amounts of damage against human units. Heroes are also able to collect relics, which grant the player additional economic or military bonuses when deposited in a player's temple. Most units can be upgraded, making them better at certain tasks.