The "Amonro World" was not ruled by the Amonros until the recent century.
This was, after all, a rather small and enveloped world. There was only one huge disastrous phenomenon that struck this world.
That was a long time ago—back in the era when the "Amonro World" was known as the "Pyrodust Wold", the Amonros were pets and livestock of another dominant species—the Lava Giants. The "great Amonros" did not have any rights at all; all they could do was to cower in the holes where they lived, or to consume the fodder that the giants fed them.
And then, the fateful day came, the day when the powerful Lava Giants found a dimensional rift that led to the "Shura World".
***
What came after was several hundred years of perilous war.
After facing a failed expedition into the Shura World, the Lava Giants were faced with terrifying retribution from the mighty Shuras. This led to the Lava Giants' severe lost in manpower and resources.