Many games make you feel you are part of a social experience when npcs give you a unexpected feedback for your actions. Such as when you finish kanto league and all tvs are talking about you beeing the champion. In other words, when random npcs will change their diolgue to match your recent accomplishment. That create a illusion that you are known in a comunity, wich prevent you from getting bored due to the lack of social reward of the game. Thats the reason mmorpg are so much adictive then offline rpgs. So my suggestion is to add tittles to the player when the player does an certain requirement, (like when you unlock a badge in a game ) and make npcs react to the tittles with diferent dialogues. So, lets say the player killed a few peoples, he will be know as not popular murder, and npc guards will have a porcentage chance to atack the player, while normal npcs will have a porcentage chance to run. The more the player kills, new tittles are unlocked, and the porcentage goes up.