"Surprise, surprise," said Lex, his voice tinged with sarcasm as he watched the broken and battered body on the floor. "A trap. Who could have seen that coming?"
Everything about Lex, from his posture, to his tone of voice and his words spoke of the fact that he was displaying a very cavalier attitude - as if he did not take his current situation as a threat at all.
The truth was the exact opposite. Lex had, in fact, spread out all his spirit and soul sense the moment he felt something odd about Ra's body. But while he heard Ra screaming, he could not detect the deity.
Unless he found Ra, there was nothing he could do to him. So, the best solution he had was to bait him.
The two of them already had animosity, and based on his experience, Lex judged that Ra was either not in his best state mentally, or he was just a very careless deity. Either way, aggravating him was the best way of luring him out.