"I can tell you information on that woman, but in return, you have to bring one of your lackeys over, I have questions for him." Benjamin requested.
The knife-scarred man already sent all his men away, only he and Benjamin remained in the sewers. Benjamin could kill the knife-scarred man with magic and no one would notice.
But he would not do this.
After killing the knife-scarred man, it would be troublesome for him to find that assassin. Rather than using force, he might as well negotiate with the opposition. After all, the assassin was under the command of the knife-scarred man, so it would be easy for him to be summoned.
Benjamin could kill the knife-scarred man after he is done questioning the assassin who will be sent away. After killing the knife-scarred man, he would find another exit and escape. The lackeys would have no idea what happened.