Kingdom of Paradise

The world of one god (also called the Christian Earth) is a dimension where only one deity exists. In this universe the Greco-Roman, Egyptian, and Norse myths are just myths and Percy Jackson and his friends only exist as characters in a book series created by Rick Riordan.

Connection to the world of many gods
The world of One god is adjacent to another universe called the "world of many gods" (also called Pagan Earth) where pantheons of multiple pagan religions coexist and where Percy Jackson, Carter Kane, and Magnus Chase are all real.

History compared to the world of many gods
In this world all the stories in the Old Testament are true. Unlike the Pagan earth which arose from chaos and whose deities are all descendent's of chaos in one way or another, this universe however was created by the One God who is uncreated and eternal.

After a certain point the history of the world of one God seems to align pretty well with the world of many gods. Demigods do not exist in this universe; but the important historical figures who were demigods on Pagan Earth have mortal counterparts in this reality. There are subtle differences of course, especially in the realm of pop culture, music and movies.

Many people who exist in the world of one god don't have counterparts on the world of many gods and visa versa. The histories start to seriously diverge however around the mid 2000's when something called the "great stirring" begins to happen on the Pagan Earth. A human on Christian Earth named Rick Riordan awakens a latent psychic power that lets him see visions of the Pagan Earth and a young demigod named Perseus Jackson begins his adventures.

Traveling between the two worlds
There are several of portals connecting the two universes that can be accessed if you have a magic key to open them. Below is a list of three known portals. The One God himself cannot cross over because it is forbidden by ancient divine laws and an oath he made himself thousands of years ago. His omnipotence does not extend to the world of many gods because he didn't create that universe. The pagan gods are also forbidden by divine laws to cross over into the world of one god.
 * 1) Constantine Arch in Rome, Italy
 * 2) Jamestown Church, Virginia, USA
 * 3) Wizard Island, Crater Lake, Oregan, USA

Whenever the One God needs to interact with the world of many gods he sends angels to do his work for him. Angels who cross over into the Pagan world will find their powers greatly diminished as they are cut off from heaven and their powers will continue to drain until they are the same as normal humans.

Demons (fallen angels) are capable of crossing over without their powers weakening in the slightest and for a price can ferry individuals from dimension to another.

Demigods who travel from the world of many gods to the world of one god will lose their powers completely and immediately and can't regain them until they return. Witches and magicians from the world of many gods will be powerless on the world of one god. Magical objects however from either universe will retain their power, which is why the keys can be used to get back and forth between the worlds.