objects.closest("Bank chest").interact("Use");    This method looks for an object called "Bank chest" and attempts to interact with it using "Use". If you attempt to interaction with the "Bank chest" using "Attack", the method will not work because "Bank chest" does not have the action "Attack".  npcs.closest("Guard").interact("Attack"); Lets say you are killing guards, as the method shows above. What happens when you kill all the guards and this method is called? You will get an error called