When battling other players in Castle Age there are two different options. Players choose to either Invade or Duel. Invade will have a

click to enlarge
player's entire army attack an opponent whereas duelling is a one-on-one battle between each army's most powerful general. Like questing, players will gain experience and levels for both invading and duelling.
Monster battles are not at all the same as battling other players. There are three types of monster battles. The first, and least complex, are boss battles. When you have completed all the quests in a land for the first time, you may then challenge the land's boss, starting with the Orc King in the Land of Fire. These are normally fairly small battles as only people in your army can help you. The same is true for team battles, but players with very few friends playing Castle Age may find the team battles more difficult. The player who initiates the battle is only given a specific time frame to kill the monster, similar to monster quests in Warlords. If the beast lives beyond the allotted time the mission is a failure.
The most epic of all the monster battles occur when players summon world monsters like the Hydra. There may be up to one hundred players of all levels involved in a battle to slay these most gruesome of monsters. Some epic monsters have special powers, like a magical shield, that make them that much more powerful. To help defeat world monsters, players can ask friends to help by joining the battle or by answering the “Call to Arms”, which brings in special assaults on the monster. The more people who answer the call, the more powerful the special assault weapon becomes. The monster battles also provide some of the best loot in the game.
All-in-all, with interesting creatures, and complex questing and battle systems, Castle Age is a great Facebook quest game that will delight any fantasy fan.