You are taking your battle action and have just declared your attackers. Your opponent now plays an action that corrupts one of your attacking units? What happens? Is that unit removed from the attack or since it was already declared as an attacker does the corruption have no affect now? Obviously your opponent could have played the corruption action after you declared the zone you were attacking, but before you declare you attackers. This could be an issue though if your opponent was trying to see what forces you commit to the attack before he/she chooses which unit to corrupt.
Thank You,
rundeks