I have never been in such darkness, I could not see my hand in front of my face. As a result I learned a few things about darkness. Since you can't see reality, it promotes a life of unreality. Because you can't see with your eyes, you have to see with your mind, which causes you to live your life out of your imagination. We also discovered that all the creatures that live deep in the cave are blind and if a creature wanders into the cave and can't get out, it will become blind.
Light is needed in order to stimulate sight.
Extended darkness will produce permanent blindness. After about 45 seconds, which seemed like an hour to me, the guide had one of the people turn on the light to his watch. It surprised me on what an impact that insignificant light made. It penetrated that darkness to the point that I could see the outline of the group. The most amazing thing is, each person in this group automatically started moving towards the light.