Takes care of those pesky bosses without all the mess. Think Hill Trolls, the Nazgul, etc. Enemies like those demand your immediate attention, and if you can't get rid of them in a couple of turns, you can quickly get overwhelmed by the rest of the encounter deck. A lot of scenarios leave you wanting a damage spike of 10 or more at some point, and Black Arrow will get you there. The 1-per-deck stipulation makes it inconsistent from game to game, but it's so good when it comes up, I don't see why you wouldn't go for it if you're using Bard the Bowman or Legolas. If you happen to be running Lore, go ahead and dig for it with Master of the Forge, but don't bother building around it unnecessarily. Just be glad when you draw it.