King Odin was born from the roots of the World Tree by the creator, Ymir. He originally created humanity from the branches of the world tree, creating the first 2 humans Ash and Embla to populate Yorthe. As the population increased and the humans became more advanced, he witnessed humanity conjure negative concepts. This led to him to believe his creation is flawed and the creator Ymir punished him for making a flawed creation. This caused Odin to split into two, the god king Sigtyr and the devil king Valtýr, which in turn caused the entire population of humans to split into angels and demons.
Cosmology
In this world the "Earth" is one gigantic World Tree split into 3 different realms, the Afterworld, Yorthe and the Underworld. Each realm is populated by a different species, those being angels and demons, which used to be humans who lived on Yorthe. Yorthe no longer exists and the great rainbow bridge now leads into the Underworld instead, being guarded by the Cherubim of the angel race. The Afterworld and Underworld are vastly different places, some even say polar opposites. They differ from eachother greatly from plants, animals even to the atmosphere.