Despite winning the fight, Arthur was still in awe. He shook his head in wonder and said, "That's just a crippled second mortal coil cultivator. I wonder what an intact one is truly capable of."
If he had a choice, he wouldn't have fought Black Mantis. It was because of that relative lack of lethal danger and the confidence he gained in researching Black Mantis that he was willing to fight it out with the man.
He had done a lot of research on the boss of the mercenary group. He only did surface-level research on the group before he got Irvin and heard that their boss was injured. It was then that he did deeper research and learned how Black Mantis was injured.
His so-called deeper research was simply paying for deep-level information on Black Mantis from an information broker. It was expensive, but it gave him the confidence to stand and fight Black Mantis.
