Honestly that would be an amazing fight! Think about it, if the Shadow God tries to take over Sunny's Soul Sea like Mordred the Shadow God would have to fight every single shadow in his soul sea.
I'm kinda hoping it becomes a forced marriage thing and they are more allies than a relationship. That way it's one less but one more of a problem with the demon faction.
So chapter 14 (Child of Shadows) says all God's are dead but the Shadow God stirs in his eternal slumber and gives Sunny a gift.. I'm wondering if Sunny will awaken him from his eternal slumber as one of his shadows.
This made the handsome young man give them the middle finger under the table, making the two beings, who were both his greatest allies and greatest critics, chuckle inside his head.
Any form, any shape. The ability to not only grasp the essence of, but also become any creature he truly came to know. The prospect of such an ability seemed… limitless.