The air in Mercuria was very thin, which could make unaccustomed creatures dizzy until their bodies adapted to it. The mountainous landscape included high mountains and deep valleys, carved by rivers that ran fast down the gentle slopes. Although flatlands and prairies were uncommon, Mercuria had several high plateaus on which most settlements were located. The entire layer was constantly bathed in golden light.
The layer also served as the armory of Seven Heavens, as well as the gathering place for its troops. It was also the site of numerous mausoleums dedicated to fallen noble warriors. Their memory was honored annually during the Day of Memory by all inhabitants of Mercuria.