The Shadow of the Law was actually the Shadow of Christ, and He came because man had sinned (because man had lost that image, he lost that light inside of him).
So, man’s “unbelief” created this impediment, this object between him and God, so that man was now living in the same shadow that his unbelief had created.
So, man moved from the Light to the Darkness; he was now living in the darkness because he chose darkness. What Christ did was come as the Shadow in order to remove the unbelief.
This is only a small portion of the teaching, “Face of the deep“.