To kill a Unicorn is to bring bad luck and the hatred of nature itself down upon the foolish. It is said that the mate of a unicorn that is murdered will turn horrible in it’s pain and anger, turning against nature to hunt and kill the murderer of it’s mate. It turns dark and soulless and seeks nothing but the death of it’s enemy.
For a creation of the Black Tide of Acqua,death never truly befalls it. As long as the most vital part of it survives,the foul thing will continue to exist. In a certain sense..
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....)