Six bytes per entry, one chosen at random by 970B: the room, the address of an exit in that room's record, and the three bytes of the exit (direction, door, destination), which are blanked out at the start of the game and restored when Elrond reads the map (A6B8). Terminated by $FF. The code counts entries from C6F7, six bytes earlier, so the first entry here is number 1.