This card reinforces one Wall to make it stronger. Play this card and place a Fortify token on any 1 Wall. A Wall can never have more than 1 Fortify token on it. When a Monster attacks that Wall, the Monster is damaged for 1 point as usual, but the Fortify token is removed instead of the Wall. The Monster stays in the Swordsman ring.
If a Giant Boulder hits a Wall that has a Fortify token placed on it, the Giant Boulder stops, the Fortify token is removed, and the Wall remains in play.