Defend the Wall is a mission in Warlord Battlecry III. It is located in Al-Diraq and the game says "Help is required once again to defend the Draqine Wall." It is a replayable mission where the reward is 80 crowns and is hard difficulty.
"The Barbarians are becoming more organized. They are building a base near the Diraqine Wall. You will need to venture beyond the Wall to stop them."