My players will get a choice as they are assaulting a castle. There will be three magical siege engines they will need to stop so their troops don't get slaughtered.
Now knowing they have a fight with the big bad coming, they can either sneak in and stop all three towers themselves, or just stop one then move in to the boss fight leaving the other two towers to their retainers.
Should the players decide to leave the other towers to their retainers I want a simple way to decide some off screen combat because the retainers might die if it's left to them. How would you guys handle it?