Gu Zhen Ren
Now the action begins. Complete ruthless slaughter just like the end of the first arc. No one will be spared except a few, who will never match Fang Yuan. Makes me wonder if Bai Ning Bing will be lied to, since Fang Yuan is known for breaking promises. The poison vow Gu will only affect Bai, so it's opportunistic.
Perfect chance to kill Ruo Nan as she can contribute some to the refinement plus get rid of a major threat. Hopefully her plot armor keep her alive cause it is a perfect opportunity with no reason not to kill her now. If she was below rank 4 sure it would be wasteful to use her in the refining but he is using rank 4 in it plus she should have a better foundation than most which seems important and A grade talent.