Dorian lost consciousness after expressing his sympathy for Arthur. Watching the man, whose hair had turned white, Arthur remained silent. His breathing grew deeper as he seemed to enter a sort of mental shutdown.
Arthur deeply regretted allowing Dorian to experience his wrath, even for a mere tenth of a second. It was evident that it was something no human could bear. This left Arthur wondering why he, of all people, could endure it.
Though he had previously attributed this unusual resilience to the side effect of his creation powers, apathy, he could no longer deny the truth. Arthur began to suspect that he was not a human but something entirely different.
Having encountered countless races within the tower, Arthur didn't feel alienated by the idea of being non-human. In fact, it relieved him of the burden of being an outcast from human society.