The world was changing and as old civilizations were destroyed and new ones were created beliefs had changed. More and more dieties were fading from the minds of worshippers as the world centered their attention to technology.
As gods were forgotten the diety would begin to lose power before disapearing forever. Panick broke out among the many dieties of the world and an emergency meeting was called, causing gods and goddess to all come together for the first time in over a thousand years.
After several heated debates they all decided that the only way to save themselves was to return to the mortal plane and gather followers.
The only problem was that they weren't powerful enough to descend from the heavens in all their glory, instead they would have to gain followers while using limiting physical forms. However the more followers they collected the more powerful they became.
With so many dieties descending upon Earth at once there would be fierce competition for worshippers.