The Lower Domain is a vast expanse, consisting of over three thousand worlds and hundreds of stars, it is divided into two distinct regions known as Yin and Yang.
The Yang region comprises three realms, namely the Qi Empyrean Realm, the Martial Rising Realm, and the Common Road Realm. Each realm can be likened to a galaxy, housing tens of solar systems and hundreds of inhabited worlds.
In contrast, the Yin region consists of two realms: the Devil Realm and the Nether Planes. Despite consisting of only two realms, the Nether Planes alone spans as large an area as the entire Yang region.
These regions derive their names from the predominant nature of the stars within each. Stars in the Yang region emit predominantly Yang Qi, while those in the Yin region are composed of Yin Qi.