The Game

So the Game is basically where players like us log in to. Yes, we can log in to our Avatars in the "real world" too, but while in Avatar mode we can access the Game. The Game is like an enormous data base where all worlds are stored in and can be unlocked by players. The worlds are not unlocked by achievements, they only unlock by their own accord when they feel the need for a hero.
If the world does not want help, no Avatar can enter it. This can be troublesome when a stubborn world chooses to ignore it's problems and keep the gates shut so none can enter. Eventually this world will be consumed by its own darkness.