To get this achievments you need to find bao in "infested fog" (1. picture) and complete side quest "just desserts" (2. picture location of cave)
1. Go to him and ask the quest. He will give you key to the "breeding grounds". You will find the boss there you need to kill.
2. Return to bao and when you finish quest and he will open you offer just buy from him make few meters around and kill some monsters and you can sell it to him back.

Don't forget to like it

Picture no.1


Picture no.2