The cultists had left their base for some time, but this wasn't much of a problem for Fang Zheng. With the keen perception of the Zerg, he quickly picked up the faint smell of sulfur lingering in the air. Following the scent, he and Fina didn't have to work too hard to find the lingering traces left by the cultists.
In fact, this wasn't difficult at all. According to Knight Conan, aside from the cavalry patrolling outside, there were a total of thirty Sanctuary Warriors inside the base. That was no small number. Moreover, the cultists didn't kill them all but took them captive instead and left. Moving so many people at once without leaving traces would have been an impossible story.
Therefore, it didn't take much time for Fang Zheng and Fina to determine the direction the cultists had left in, and they tracked them down without delay.