As you defend the castle, you can only pay attention to the enemies approaching on one of the four paths at a time.

At the beginning of each Engagement, place your hero card below one of the four paths. This is your hero’s current path. You can only apply hits to the enemies on your path (Range is also a factor).

At any time during the Strategy phase, you may change your path by exhausting any ready or unapplied die. Then, move your hero card to below any other path you wish. Going forward, you can attack the enemies on the new path instead. To be clear, you may even do this in the middle of applying damage. Say you generate seven hits, but it only takes three hits to eliminate all the enemies on your current path. You can apply those three hits, exhaust a die to change your path, and then apply the remaining four hits to the enemies on the new path.