Actually, the others at the Yuwen Mansion were of little consequence. From the moment Zou Feng captured Yuwen Zheng, the upper hand was his.
In short, as long as he held Yuwen Zheng hostage, Yuwen Boxi would have to obediently comply with any demand, provided it was within his power to do so.
Of course, Yuwen Boxi wasn't a fool. The others could be released for now, but not Bian Yixia.
Anyone could see that he had to keep Bian Yixia as a bargaining chip for Yuwen Zheng...
As for Fu Zhouchen, he naturally had a corresponding Communication Magical Artifact to inform Yuwen Boxi.
This device, called a Communication Jade Talisman, was clearly another tool exclusive to the circles of High Grade Martial Artists.
The Communication Jade Talisman could only display a few characters at a time. The holder of the other half of the Jade Talisman would instantly see the message, as long as the distance between them wasn't too great.
