Make the invoke effect of the Tsurugi of Muramasa enhance it to give double damage for a limited time, but also become bloodthirsty during that time. For an immediate effect, it could also cause fear when invoked.

The Tsurugi of Muramasa should act bloodthirsty like Stormbringer does, because historically all swords made by Muramasa were reputed to be bloodthirsty or traitorous.

Remove Stormbringer’s automatic attacking of peaceful monsters and instead incentivize attacking peaceful monsters by giving the hero some benefit, such as lowering prayer timeout, whenever attacking a peaceful monster with it.

While you are wielding Stormbringer, you gain alignment for killing peacefuls and pets (rather than losing it).

All Banes artifacts are bloodthirsty (disabling the attack prompt for peacefuls, like Stormbringer) versus their respective monster type.