I think it'll be a nice addition to add in the "ancient mace" this would benefit mostly the pk community and also reduce the amount of 1 item "spec n run" people who try and kill you.
If you don't know, the ancient mace special attack can hit through melee prayer and drain the opponents prayer by 100% of what your special attack dealt.
For instance, if player A has 50 prayer points and player B uses the ancient mace special attack and hits a 30, player A prayer points would be reduced to 20.
The item however should not be easily accessible, and should come at a cost for people running around with it. Maybe adding it to a boss drop or even a new quest, which is difficult to complete, and costs 5 million + to buy back when dead.
I just feel this could be a good way to discourage the 1 item pkers who run in and spec and leave, maybe make them think twice since there is now a possibility they could be caught and punished.