They have made this battlefield thing a little confusing. To me that whole map would be the battlefield and then each area you can enter would be a dungeon. I.E. BF 1 Dungeon 1, BF 1 Dungeon 2 ......
Anyway, You find the large keys you are unable to pick up but give you access to the different levels of the BFs. I already had access to BF2 and found another key that gave me access to BF2. Does this sound correct or is there a problem? Thank you.