The scene is a land called Valistea, strewn with mountains of magical Mother crystals. These crystals allow people to live in comfort thanks to the exuded ether, but they have also caused strife and wars.
The protagonist of the game is Cleve Rosefield, the firstborn of the ruler of the Grand Duchy of the Rosary. Cleve protects his younger brother Joshua, the Phoenix Dominant. Dominants are people inside whom the power of Akons (familiar to a series of summons) lives. Joshua also received some of the Phoenix power through the blessing. Jill Warrick, a political hostage from the Northern Lands, grew up with them.
In different countries and kingdoms of Valistea, Dominants are treated differently. Somewhere they are considered the upper class, in other places they are simply sent to war as living weapons.
So far, this is all that developers can share. New information will be available next year. Final Fantasy XVI is being developed exclusively for the PS5