They had killed hundreds of creatures in these 30 days, including more than 20 Shadow Bees. Even the Black Python which ranked 15th and the Spur Rhino which ranked 14th were killed by them. They had killed many unknown creatures as well.
30 days was not long, but it was like centuries for both of them, who had experienced a lot of gory battles over this period. They had become stronger than before, especially Chen Mu. He showed rapid improvements in every aspect. In the Federation, there were only a few battles that would require him to get involved personally. However, he had fought hard battles in the Hundred Depths every day. The days were filled with killing and life or death experiences. These 30 days of hardship had refined Chen Mu as if he had been reborn into a new person.