Or grind it into powder, throw it over them, and then fill then full of bullets.
On rarity, it's something everyone can get, for +2. A +1 for rarity is form something only some people can get. Just like having a catch of, say, gold. Sure it expensive, but everyone can conceivably get some gold to satisfy your catch.
Examples of +1 rarity catches are things like "Inherited Silver", "Necromatic Magic", "Items of (true) faith", etc
Things that plenty of people have but getting your hands on some may be very difficult.
And +0 rarity catches are things that are very hard to get your hands on, like "The bones of the little finger of my left hand, in my safe deposit box in a bank in Jakarta (which you don't know about)."