Here you can challenge another Kingdom to a castle battle.
The attacker attacks the castle with their catapult. Then, the castle defender(s) come out and attack the enemy catapult. Damage done is determined, for the attacker, by type of catapult, and roll on the die/dice. Damage done is determined, for the defender, by rolling a single die per each defender (maximum three, depending on the number of members in a kingdom).
If the castle is destroyed, the attacker gains 2 gold bricks.
If the catapult is destroyed, the defender gains 1 gold brick.
You can use gold bricks to purchase new catapults or castles (only the king, however, can purchase new supplies for their kingdom).