I initially thought they would have a generic villain and hero interaction, but instead their relationship is more like a neglectful parent and his child. Since he was raised in isolation by his master, he had poor relations with other Pipers despite claiming to be their ‘shepherd’, and is generally easily irritated by people while simultaneously being secretly sensitive to their perceptions of him.
His master took on a deceptive identity while raising him, so it is a strange detail that when interacting with Wren, he never at any point deceives her or pull cruel tricks on her, but explains things as they are. He has his own secrets, she has her own, and he never really forces anything out from her. He even gave clear instructions on how she was to be taken care of to the point where she found the continued good treatment to be ‘puzzling’.
Be Good, don’t die, just stay here and out of my way because I have work — that kind of attitude.