Souls

When humans were created by the combined elementals gave them something more : a soul.

When the duradin and the alran were created the elementals of earth and water, not wanting to be out done gave them souls as well.

Souls can be given to a being (called a god) by believing in it via a form of channeling. If the being does not exist yet it is created this way but if the newly created god is much like a previous god they can join the more powerful pre-existing god.

Gods die if no one believes in them any more and to become more powerful they have to act like politicians to gain more supporters while not losing they core base.