Eisen and Brody were standing in front of the boss room together. According to Bree, it was most likely to be some kind of massive worm, and considering the amount of mana that should be gathered on this floor, and the overall density of the mana that could be sensed, more than 80% of this floor's area was taken up by the boss 'room'. Rather, it was more accurate to call it a 'field', since it was apparently pretty massive. The rest of the floor that they had traversed so far was as big as the 9th floor after all, though the monsters were a bit easier to deal with.