On the Thrall Warhost's warscroll it says "in your hero phase, pick one unit from this battalion that is within 12" of an enemy unit and within 18" of the coven master. The unit you pick can charge as if it were the charge phase, and then pile in and attack as if it were the combat phase. This does not stop them from charging, piling in and attacking again later in the turn".
Does the piling in and attacking as if it were the combat phase, allow for the enemy unit to attack back? And does it mean other enemy units within 3" can pile in and attack or do they have to wait until the actual combat phase to pile in?