No, or perhaps, God always existed. It's just that amid the activities of deities and mortals, they were invisible to each other. The gods might be pondering their own existence, like the God of Stillness who started as a contemplative philosopher. But then, when too many people got involved, they suddenly became visible, and thus began to understand the world.
And the way to understand the world is... still like the sculptures of the God of Stillness, fighting each other while causing chaos.
The relationship between mysticism and the real world can be simply explained.
Before people discovered mystical incantations, the mystical planes already existed, just unknown to reality. When someone found that reciting incantations could summon a dog from a book, mysticism was born. The planes connected, creating some "theological reactions."
