New spell idea the smoke spell

My idea is a new spell wat would be a smoke spell by using this spell it would give you a limited time when troops walk through the smoke and the defence would not be able to target your troops untill the smoke has cleared simple and easy really to get the idea of how it would work u would say the spell had a area hit range all depending on lvl of a max of say 10-15 squares but the air blower defence if dropped in its area and blower is pointing in the right direction would clear the smoke spell quicker

boom beach? where?
but the blower utility is good idea