As a result, the humans in the immortal realm were stationed in a "small" area and didn't dare to explore outside easily.
Of course, it was just relatively "small."
The birth of every immortal king would open up many areas suitable for humans to live in. Even if the immortal king wasn't born of the human race, those who lived in those areas were still humans.
Firstly, the immortal kings didn't mind what kind of living beings lived there. Secondly, those who obtained the inheritance of the immortal kings and could produce the next generation were usually humans.
Many living beings in the immortal realms were originally innate spirits.