the collective unconscious
The collective unconscious, or collective shadow, is usually the most difficult to describe in words. It's the realm that the archetypes inhabit, which is to say that it's a realm of spiritual possibilities captured in symbols and images.
Perhaps for that reason, I find it easier to picture the collective in images than to describe it in words. One image I have is of a deep pool in a subterranean cavern far beneath the surface of the earth.
Just as the social unconscious consists of traits that are in shadow for a group or culture, the collective unconscious consists of the traits that are in shadow for all human beings.
What does that mean? Most of us in Shadow Work would say that most of us have most shadows, at different degrees of intensity. We've noticed that when one person is working their issue in a group, most the people witnessing it say afterward that they recognised that same issue in themselves.
Thus, one way to describe the collective shadow for all humans is as the shadows that we all share. For me to believe that we don't all share them would suggest that a person exists who has no shadow. This person never suffered a loss of self-esteem, carries no grief for a lost loved one, is in complete control at all times, and has accomplished every personal goal. If there is someone like that, I'd love to meet him or her! But my own personal belief is that no one like that exists because having shadow, and healing it, is part of our purpose in life.