Yes, a Nature keyword would be fit.
On account of its pros and cons, I think it's strategically better to have only Bloody Moon in hand. Quarry loss won't affect much the opponent. If the opponent is playing with Unliving and Titan keywords, he will already have a high quarry from the early stages of the game, or else he will have massed a large amount of bricks using xProduction Unliving and Titan cards.
Otherwise any other deck just masses up bricks, without using them often, therefore reducing the Quarry won't affect much the opponent as they will be able to mound a good defensive easily after 10-20 rounds (= averagely 70 bricks produced in total).
However damaging the enemy's Dungeon, is usually more crippling as most decks use up a lot of recruits and/or gems. Facing an opponent who bases his attacks on recruits is much more common, therefore having only Bloody Moon is the most cost-efficient solution for a deck.