Heavenly Beings that grew by progressing Science to its limit under the guidance of Gods, who acquired knowledge from the Creator of All Things.
Demons that grew by taking over strong magic under the guidance of Devil Kings, who got power from the Creator of All Things.
Between those two races, humanity barely survived by relying on the technology of the Heavenly Beings,earned through belief, and the magic of Demons, earned through sacrifice.
That is, until the day of the [Science Revolution] in the year A.A. 1728.
By spreading the knowledge about the core of the Heavenly Beings' technology, which is the creation of energy from burning the Worldstone, humans declared independence from both Demons and Heavenly Beings to evolve further. And as technology that only requires a Worldstone as a medium became common in daily life, magic that requires life for power slowly faded away.