Nightfall is the latest full "chapter" in the Guild Wars series of games. Many players think it has the best story. Nightfall introduced "Heroes", which are computer-controlled companions that the player can equip with items and skills, so that you can play the game by yourself if you so choose (although it's much more fun playing in a well-coordinated group, or guild. Since the Guild Wars games don't have a monthly fee like most MMO's, a parent doesn't have to be too concerned if the kid gets bored with it for some reason after a few months and stops playing it (it won't be a continual drain on your credit card).