- Symbols: Water and courage
- Capital: Athantis
- Ruler: Enrique the Golden King
- Characteristics:

Home to pirates and adventurers, Poseia is a nation of merchants with well-developed businesses and banks.
Many of Poseia's sailors are experienced and knowledgeable about ships, and the nation owes its wealth to its advanced navigation skills and the establishment of trade routes.

One unique aspect about this nation is that it is where "Aqua Stones," a mystical blue stone slightly translucent and imbued with water, are created. Contrary to its name, however, it actually pushes water away, making it possible for heavy objects to float.
Because it changes shape when in contact with magic, it is easy to work with and widely used to construct ships and buildings.

It is also what gives the buildings of Poseia the characteristic blue glow.
Even after airships have already been commercialized, Aqua Stones are commonly used to this day when producing magical items in Poseia.