.E## holds the foemap (enemy-map) for a map.
It's exactly like .T## in format (with a single layer only), instead of w*h tile indices you have w*h formation set numbers.
The data at a given x,y location specifies what formation set will be used to decide the formation you will fight if you get into a random battle on that tile. It is the formation set number +1. If the value is 0, then no random battles may occur from stepping onto that tile.