Black Bead monks are generally nonviolent, but if they sense that there is no other recourse they are adept fighters. Their fighting style focuses around denial - they deny their opponents sight and the ability to perform various tasks they are used to being able to do. Make good use of the Darkness ability to position the four monks well.
Black Bead monks are not materialistic in any way shape or form - they believe material possessions get in the way of enlightenment. Believing even that seeing material possessions will tempt them, they train themselves out of the notion of sight.
Black Bead monks are extremely proud, and extremely decisive. They are often called upon to be arbiters of disputes, being completely impartial and choosing what is often seen as the fairest outcome. Each monk may have their own unique quirks, but that is generally how they are seen.
Or maybe they're just...bad guy. You're fighting them because they're in the wrong and you need to stop them before they stir up more trouble.
