Wounds up to X opponent's BACK ROW units, starting across.
Every point of Defense a BACK ROW unit has will block one Arrow. Every unit wounded by Arrow will use up one Arrow.
Arrow will attempt to hit a unit until it succeeds or runs out of Arrow. Once a unit is hit, any remaining points of Arrow will go down the opponent's BACK ROW and keep trying to wound units.
17 units have the Arrow ability: