War is a constant in many RPG’s. I believe that I have done enough war based adventures and campaigns that I might as well share some ideas and open the stage for others to share their thoughts.
You receive a vision of a rooftop "somewhere close by", where a rare moss grows; in the vision, you know the moss is suitable for greatly enhancing the effects of certain types of potions. Now go and find that rooftop. Don't fall off. (Of course, rooftop runners *will* be taken for miscreants by the local City Watch....)