Mortals reign in the Stream. They are born and build cities, write novels, fight and die - in general, they use the time allotted to them to live as they want. They are creatures of cycles, so they understand what hunger and sleep are. They see sunrises in the morning and wait for sunsets in the evening. Winter is followed by spring, and summer is followed by autumn, and this is no surprise to mortals.
Every mortal, regardless of their worldview or religion, knows that they are the essence of Shang and La. Their body is La, a temporary container for the soul that will leave the smoldering flesh after death. Shang is the name given to their soul, which is an amazing and multifaceted entity that gives a creature personality and sometimes supernatural abilities.
Two types of intelligent beings exist in Shan-La: humans and sahash. There's a chance that there are others too.