The Light shines in the darkness, and the darkness did not comprehend it.
— Book of John 1:5

Just as some of the people in our dreams can represent the light, others can represent the dark.

In our nightmares there are figures that creep from the shadows and only a sliver of a silhouette is revealed.  Often when we wake we have trouble remembering who they were or what they represented.  The underlying meaning gets lost in the shadows.