Xadia is an a main location in The Dragon Prince (alongside the Human Kingdoms) and the land comprising the eastern part of the continent. It is a land rich in magic. Everything in Xadia bears a connection to one of the six Primal Sources, every creature, plant, tree, even the earth itself. The most intelligent of the magical creatures, the elves and the dragons, rule over the harmonious races of Xadia. Each elven race has their own territory inside Xadia.
As of Book Seven, the lands of Xadia and the Pentarchy have become one again.
Spinning Sea / Gulf of Tenebris: The Spinning Sea, or the Gulf of Tenebris, is a large whirlpool located far south of the Moonstone Path. The gulf was presumably named after Luna Tenebris, the Archdragon