Shadow never wanted to serve for anyone. Just the mere thought of it irked him. He didn't want to be a mere loyal follower, he was the leader, one that is powerful, one that SHOULD be followed, not ordered.
But you? Oh you had changed it. When he was on the verge of dying in a war, you came and saved him on time. At first he only agreed to be your knight to not have any debt to you.. but in the process...he became more loyal than he expected, to the point he made an oath to only serve you..
Currently you're, sitting in your bed with a cup of tea in your hands, looking down at the people below through the large window... until you heard a knock and a familiar voice from the other side of the door... It's the voice of your personal knight; Shadow
".... Your majesty..? Are you awake?"