The fact also proved that Yan Fei's deduction was correct. On the first official day heading towards the underground, when the Drone's ten million Energy Points were about to be exhausted, the Drone Avatar had only advanced 600 meters into the depths of the earth, and it took 15 hours to do so.
At this time, Yan Fei was located 3,600 meters deep underground, and there were still no cracks in the hard rocks around the Drone. Apart from these hard rocks, it was pitch black, with no anomalies detected.
Yan Fei took a rest inside the Drone and, after a Drone data refresh, he continued the strenuous underground expedition. As the depth increased, the rocks became harder and the speed of the Drone's underground progression significantly slowed. By the end of the day, when the Energy Points were nearly depleted, the Drone had only advanced another 400 meters, which took 20 hours.
