Celestial Emperor is a Lifestyle Player! CELP

The Celestial Emperor who stands above all, the one who can do anything he pleases is bored. So he decided to try to do something no one has ever done before. Breakthrough once more and escape the firmament. His 100 followers follow him in his attempt but what is this? Why are they all in a mortal plane in the body of someone else? What is this "Gods Within" everyone is talking about? What exactly is happening?