Shadow

Overview
Shadow is the child of Darkness and Light after Darkness became too old and started disappearing, Light was shown to be alive inside of Darkness all along, she gives birth to Shadow and then dies as she does. Shadow is a reborn version of Darkness and Light, without any of their past memories. They are both in control and can split apart to become two different beings, and can combine whenever they wanted to. If they go too far from each other, they would begin to deteriorate and would die.