Is not the shadow card whatever card happens to be at the bottom of the deck when you have shuffled to do a reading? Thus, different every time?
Your own shadow:
Your “shadow” is the part of yourself you do not acknowledge. That can even be good bits, if you have a poor self-image.
My daughter, who is completely unmystically inclined, said something very mystical this morning. We were standing together in sunlight, casting long shadows across concrete. She looked at her shadow, and said: “If you look at it right, your shadow is your friend for life. It is always there. You might as well get to know it.”
I was impressed.