The shadowy part was a corner of the cave where a puddle had formed from water constantly dripping from above. The dripping sound suggested a small passage or alcove within the cavern.
Igor had carefully observed that spot earlier. He found that not only was it pitch-black inside, but its surroundings were also completely dark. If it were an opening to the outside, there would be at least a faint glimmer of light, but this shadowy area was entirely obscured in darkness, without the slightest hint of illumination.
This oversight, coupled with the presence of the puddle, led Igor to dismiss the idea that this spot could be an exit.
Igor reasoned that since they hadn't encountered any puddles when they entered, this spot where a puddle had appeared surely had no connection to the exit.
Similar preconceived notions affected Kuren, causing him to overlook the shadowy corner as well.
