Gu Zhen Ren
It's possible that Bai Ning Bing has an Immortal Gu with her. We've seen a few cases of Rank 5 Gu Masters with Immortal Gu just like Fang Yuan and Hei Lou Lan. Plus BNB was previously a member of the Shadow Sect when the sect was prosperous, so she could still have Gu from the Sect. On that note, if the four remaining members of the Sect are headed to the Southern Mountains, they might seek out BNB to retrieve any leftover Gu or could even raise her back to Rank 6 for a while.
A mere little extreme physique, who cares, can his physique be compared to the mc's physique? Of course not. Pathetic. It used to be something awesome, now it's just slightly better than what normal gu masters get. Well, who cares. I shouldn't read the comments when this guy shows up, some trap lovers just start yelling and gets excited about nothing. It's annoying.