Those battlefields aren't MP. They just allow you to kill an endless amount of monsters. You can only enter them with a char who has beaten the game, and then there are infinite numbers of battlefields with the monsters going up in level along with you so you always should get good exp. And you can then endlessly level your char (till you die of boredom, that is <img src="/ubbthreads/images/graemlins/tongue.gif" alt="" /> <img src="/ubbthreads/images/graemlins/winkwink.gif" alt="" />)
