When you attack castles on the world map, depending on the soldier type and strength your army usally comes back with loot. (Usually some food, wood or stone but occasionally rubies on RBC-style targets). To attack you need to recruit an army in your castle's barracks. You should send an army out with siege tools to increase the chances of victory. Plundering loot is a great way to provide your castle with resources if you are lacking a particular one. Sometimes you need to attack a castle to complete a quest or mission. The higher your level and the more soldiers you have, the more loot and glory points you can obtain, if the castle can gain your glory..