How do castle cards work? What do castle cards do? Generally, they make your castle harder to attack.  Each card works differently, so read the card for details. When do I play a castle card? You can play a castle card as your special card on any turn.  Play it under a fortification card that doesn't already have a castle card under it, as long as that castle isn't under attack.  Play it face-down, showing it isn't active yet. How many castle cards can I play? One for each fortification card you have on the board.  So, a size three castle can have 3 castle cards. When do I pay materials costs for a castle card? Whenever you flip it face-up and activate it.  You can do so on the same turn as you play the card, but it's often better to keep your opponent(s) guessing.  The card cannot take effect until it is paid for and flipped over, but once it's flipped, you don't have to pay for it again.