You don't need any more.
if you are behind one of your walls with a range attacker can the controler of the wall fire from behind the wall. like with drake, archer, and the prince. with the elves?
All cards block line of sight. That means that archers and Prince Elien cannot shoot from behind a wall. The Fire Drake, however, is an exception for he has a special attack that hits all cards in its range regardless of line of sight.