The Creator

The reason why the tribulation happen is because the resentment of humans enslaved by Gods and Demons had reached to a boiling point that it angers the Heavens as it was foretold in the songs of Oracles and the carvings of the shamans

And that is when Elkar learned that there is a being called the Creator. 

It had many names as people and demons alike worshipped him in the past and some of those belief still persist today

The Church called this being, Light and it is to Him who the Church offered prayers and wishes. 

The Demon Church called him the Father of Morningstar, the One that sits upon the Almighty Throne.

Some tribal people called him the Source. 

Regardless of where it was and when it was, this being had been worshipped since the beginning of humans and demon civilization with so many names and so many stories.