Why does lcb Ishmael use a mace? (Potential "evil defining" canto spoilers)

I know the shield represents the shield from her base ego, but why a mace instead of something like the harpoon she carriers and sharpens? I understand if she doesn't want to use the harpoon since she may associate it with trauma, saving it for "that bastard", and always wants it to stay sharp. But why a mace of all other Potential weapons she could have found or have been given? Since the weapon a sinner has, as far as have been seen, a strong tie to their past, but Ishmael looses it in her base ego, does that mean she has connection to that mace of hers? Sorry if it was already explained somewhere and I missed it because i only looked it and searched for a little bit before asking.