Now the question are, if Nine has been surviving by himself for at least a decade, why he was on the verge of dying from hunger when Melissa found him and why were the werewolves after him and cut his tongue and fangs after so much time has passed?
By the way, i think there is another possible way to break the box: The sword buffs her up to max stats but the hits with it rebound, so she just have to grab the sword on one hand and a normal maul or mace on the other and smash it open.