Twenty Kingdoms

Clover: If we assume those people were wiped out by some "enemy," it means those enemies should have survived later in history. Coincidentally enough... 800 years ago, at the end of the Lost 100 Years, was the precise birth of today's "World Government." If the enemy of those eradicated peoples is our World Government, then the "Lost 100 Years" could easily be a piece of INCONVENIENT HISTORY that the World Government needed to stamp out...!!! From the ancient writings of the few Poneglyphs we HAVE found, we have learned of the existence of a nation... One which no longer exists in any form, but still appears in those messages. An ENORMOUS KINGDOM...!!

They seem to have held great power once, but the information about this kingdom has been carefully erased. As they knew of their imminent defeat by the alliance that would later be called the World Government, they carved the truth into stone, to give to the future. Those are the Poneglyphs that still exist today...!!!

- Clover, explianing about the Ancient Alliance. Chapter 395

Pappug: Because they have the blood of the Creators in their veins...... Eight hundred years ago, a group of twenty Kings... ...formed a mighty organization known as the World Government.

- Pappug, on the World Nobles. Chapter 497.

The Twenty Kingdoms or known as the Ancient Alliance are the twenty kings of their kingdoms combine to become an Ancient Alliance that became the World Government. During the Void Century they fought against the Ancient Kingdom, by 800 A.O.S the Alliances became the World Government. The World Noble are descended from these kings.

First mentioned in chapter 395 by Clover as the "enemy" of the Ancient Kingdom or simply an Ancient Alliance, they were fully explained 102 chapters later by Pappug. Why or how the Twenty Kingdoms overthrew the Ancient Kingdom is a mystery.