The Undead King Arthur had to stop Adrian because he was going to get another being that was just observing. It might be rude to stare but any sign of aggression from them might mean that they want a fight. Adrian is currently fighting the three mythical monsters at the behest of the Undead King. Any act that he does will reflect on the undead king himself.
"I got to carried away. My apologies." Adrian stated as he told Charon to stop everything.
Charon agreed to the commands of his master and only stopped when Adrian told it to. Even the presence of the undead king did not make Charon stop. This means that Charon would have continued and killed the three mythical monsters if Adrian was not satisfied.
