The Aetherial Expanse

"May your waters be ever calm and your sails ever full. May the stars shine brightly to light your way in the dark. And when you pass may you rest peacfully on the aetherial shores." -An old sailers blessing.
The Aetherial Expanse is more than just a great sea, it is the universe itself. Here, the vastness of the open sea and the vastness of space are one and the same. Every landmass is a planet unto itself, and every island its moon. Large plates of land float in the waters of the Expanse and can almost be seen as solar systems in terms of astronomy. These plates are massive and stretch for thousands of miles, with dozens of landmasses and potentially hundreds of islands dotted around them. The ends of these plates mark what is known in the Aetherial Expanse as the Deep Waters, portions of the expanse that descend infinitly into the void of existence. The Deep Waters are the most dangerous and bizzare part of the Expanse, as they are home to creatures that crawl in from outside reality. Yet dispite their danger, the Deep Waters are frequently traversed as explorers, traders, pirates, and settlers travel between the plates. Some would say you aren't a real sailer until you have sailed the Deep Waters at least once.
The Expanse is home to many empires, kingdoms, city-states, and settlements, all trying to expand and thrive in the vastness of the Expanse. Some subsist off of trading, while others thrive off of conquering. The expanse is an ever changing landscape filled with opportunity and strife alike. The immensity of the Expanse, alongside its everchanging nature and constantly adrift landmasses, makes charting it extremely difficult. Charts must be constantly maintained and updated, lest they become obsolete. Therefore, maps older than a century that chart the location of larger landmasses are essentially useless. This ever changing nature means that some landmasses can become hidden or, in the lesser explored regions of the Expanse, even lost entirely.
The waters of the Expanse are a haven for pirates and other lawless individuals. The ever expanding nature of the civilizations that inhabit the landmasses, along with their constant need for trade and conquest, make the life of a pirate a particularly lucrative one. Most inhabitants don't see pirates going away anytime soon. The constant shifting of landmasses grants anyone hiding from the law places to stow away, as many smaller landmasses are hidden or lost to the known charts of the Deep Waters.

An island port city off the coast of a greater landmass.

Type

Dimensional plane

Technology in the Aetherial Expanse advances more slowly than one would expect. The greater Expanse as a whole has been in the colonial era for around 300 years, and it doesn't seem to be advancing any time soon. Guns such as wheellocks and arquebuses are commonplace, but very recently flintlock weapons have been popping up, as they are newly invented by the Empire of Vastello. Through a combination of the Vastellan empire's aggressive expansionism and piracy, flintlocks can occasionally be found elswhere in the Expanse, but they are by no means common outside of the Vastellan military.