Exactly what are arrow counters? Are they from one of the Ascension sets (I haven't played all them but haven't ran into that term)
Or do you just some sort of marker to track the arrow counters and when they are gone, you place the card in your discard pile?
It's any marker that you have handy -- coins, cubes, meeples, arrows from Bang: The Dice Game, etc.
Once they're used, you place the card in your discard pile (a.k.a., "destroy").