There is an unwritten rule that cultivators at the Golden Core stage and above are not allowed to step into the Monster Beast Forest to hunt monster beasts.
This is to prevent catastrophic devastation to the Monster Beast Forest. To mortals, monster beasts are demons and banes; but to cultivators, they are supreme treasures and cultivation resources.
The blood of monster beasts can be used to make talismans. Their internal organs and parts of their flesh can be used to refine elixirs. Their hide, armor, bones, and teeth can be used to forge weapons. Even more precious are their Monster Cores and monster souls—demon cultivators can use Monster Cores to boost their cultivation bases, while monster souls can serve as artifact spirits for Spirit Tools.
Chapter 153