Han Li was extremely vexed when his swords proved completely harmless to the demon cultivators. But after some thought, he regained his calm.
A vast majority of high grade demon beasts specialized in cultivating their bodies. Their dense flesh and hardened skin could rival the magic treasures of similarly ranked cultivators. Furthermore, demon beasts had lifespans that lasted several times longer than common cultivators, sometimes possessing lifespans that were tens of times longer. As a result, the higher grade the demon beast, and the longer they cultivated, the more astonishingly durable their body would be.
Before arriving at Nascent Soul stage, cultivators relied on their magic treasures and knowledge to slay demon beasts of grade seven and under. But once demon beasts reached the metamorphosis stage at grade eight, they would often suppress human cultivators of the same rank with their cultivated bodies and expanded intellect.