The long staircase near the entrance to the cave is the site of the boss fight with Borghen, but that won't happen until you retrieve the Goddess's Bell. The layout of the floor is quite simple, with the two Treasure chests resting not far off the beaten path. You may notice a door in the southwest corner, but you cannot enter it. This is the exit of a shortcut back to B1 after you've obtained the Goddess's Bell. Since you cannot cast Teleport here, it's a lifesaver.