Event dispatchers spring to mind 
You can send out an event dispatch call to your game instance, then when you spawn your npc’s you bind to that event dispatcher so that when it is called, everything bound to it gets notified of it being triggered.
Event dispatchers spring to mind You can send out an event dispatch call to your game instance, then when you spawn your npc’s you bind to that event dispatcher so that when it is called, everything bound to it gets notified of it being triggered.