The Golden City is the name of the world of angels. When the deities first arrived in the world, it was devoid of any intelligent life. It would eventually be populated by the angels who were created by the former God of Fire, Elaith. Like the demons and their world, the angels are tied to the Golden City.
After the deities first arrived, they found the world absent of life but was abundant with magical life energies, suggesting it once housed powerful beings. After the deities were forced off the world now owned by the demons, Elaith sacrificed his diminishing life force in order to spawn a new race, the Angels.
Unbeknownst to them, the angels were driven by Elaith's will to seek out the demons so when they first interacted with each other, they inevitably came into a conflict that would leave millions died on both sides. Despite their claims of superiority, they have yet to gain traction in their war.