There were only four people present in the hall at the moment. Excluding Arthur, the other three were Cynthia, her daughter and Duke Ashborn.
Raven had excluded Cynthia from this command, which meant he only wanted him to kill two people. One of them was Duke Ashborn and the other was Cynthia's daughter.
Duke Ashborn was important for the Kingdom of Camelot. There were things about Duke Ashborn that only Arthur knew. His importance went beyond the Kingdom of Camelot.
Many people thought that Duke Ashborn's was a commoner who rose to the position of a Duke, establishing the Ashborn Family's foundation in Camelot.
However, only Arthur knew the reality. Kierre Ashborn was neither a commoner, nor was he from Camelot. His origin was much more dangerous than his strength.
For his people, Arthur was willing to kill Duke Ashborn, but he wasn't the only person. There was also Cynthia's daughter!