A Bonus Card is obtained during the Conquer the World Campaign by either buying one from the Bonus Card Shop, gaining victories in battles in the Thrones & Patriots expansion, or trading from another nation. Each card has a different ability and are different in colour. Two different cards, Pink and Blue have different effects. Pink Cards can be used on the map, whille blue can be used in battle.
Note that if a nation is defeated, the victor will obtain a Bonus Card that contains the defeated nation's powers.