Withering Heart was described in great detail in Lunatic Guan's chip, enough to make Ye Chong suspect that it was one of Lunatic Guan's own inventions. That was how Ye Chong managed to identify the drug the moment he smelled it.
Inhaling Withering Heart carelessly, even in small amounts, would have highly detrimental effects. For someone who knew so much about Withering Heart like Ye Chong, he was aware of the consequences.
Since his life was threatened, Ye Chong retaliated.
The truth was, Ye Chong was not too angry about it. These situations were normal for him. On the contrary, he was feeling very calm. He was more interested in the motive behind the woman's attack. His reckless killing in the past had taught him much, and he had since learned to think before jumping to conclusions. Besides, this woman was most likely from May's Night Ridge. He was not intimidated by May's Night Ridge per say, but Lunatic Guan had asked to visit the place, so he decided to tread with care.
