The Bandit Quest Date~
There were three types of ways monsters were born in this world. The first was dungeons. Once discovered, a lord of that territory would inform their king. Then, the kingdom would create a city or town, depending on the size.
Another type was monster caves, which, although they seemed identical to dungeons, would only have one floor, maybe two at most, and after someone destroyed their core, they would never regenerate or spawn monsters again. Meanwhile, dungeons would keep spawning monsters but considerably weaker and under the control of whoever first cleared them.
The other were naturally born monsters, which were not bound to anything and wouldn't become drawn to the dungeon or demon king without reason. Not to mention, many of them could also have harmonious lives with humans and other races if the attempt to communicate were successful.