Shadow is often linked with negativity. Various religious and literary works have symbolized Shadow as the evil which consumes everything in its path.
But I like to think of shadow as something more than evil. It provides relief as well. Cliche example is that shadow provides us relief from the sun!
Shadow can also be linked to darkness (which also has the same connotation of evil), and darkness to the universe. The universe holds so many mysteries yet to be solved by us. So maybe Shadow too can be mysterious in that way?
What do you think? Let me know in the comments!