X-Rank
A few hours before Barnabus teleported to the Fire Mine, William and Carl had left through the front entrance. A few Golden Core Cultivators noticed them, but with William's newfound strength, they didn't stand a chance.
Before they could even cry out in alarm, each of the Cultivators was struck on the back of the neck and knocked out. Their Space Rings were stolen, and William wiped every tracking Array attached to their belongings before leaving.
He thought about killing the Cultivators, but after sensing a trail of consciousness leading in another direction, William thought better of it. According to the System, the trail was some sort of Soul Link, which usually went to an Artifact someplace else.
If the thieves were killed, the Artifact would probably warn the Thieves' Guild and he would probably be attacked again. Given that they were in a hurry, William didn't have time to fight head-on with the Thieves' Guild.