This isn't too dissimilar from the Covenants in Dark Souls, which influence the way players match with each other. When you kill an NPC or commit other heinous

This isn't too dissimilar from the Covenants in Dark Souls, which influence the way players match with each other. When you kill an NPC or commit other heinous acts, you gain Sin, which any players of a given Covenant can "invade" your world instance at random anytime they want to punish sinners. This covenant system created a deep and engaging playerbase. I've not seen any other game pull such a system off, but it was fun. If the risks and rewards are right, it can work.