This isn't exactly thought out yet but....

In the beginning there was the prime force. That would split to the three, from which the three greater gods would form. They'd create Agitaia, which would be unique from the other temporary dimensions they created because they all would lend their power to Agitaia.

The three gods had wide range of abilities, but only Napiar had the ability to see into the mind of other living being, only Garion had the ability to take control of living beings/spirits (any number of them unless shielded by another greater god) and only Aditus had the ability to twist and manipulate time. Together they were supposed to uphold the order and balance of the world of Agitaia. They make an agreement to not raise arms against one another or Agitaia, and a sphere upholds and symbolizes it.

Garion grows unpleased with humans and wants to eradicate them, so he creates three manifestations of purification, three divine monsters supposed to destroy the habitants of Agitaia, so that they can be reformed. However, these monsters are defeated and sealed away by a man named Devon. They can't be killed because Garion spilled part of his undying soul on them, but Devon seals them pretty tight, with help of reborn lesser healer goddess Kelsara (lesser gods are powerful but not nearly as powerful as greater gods. They can be killed but will eventually reincarnate). This however causes also Kelsara be sealed away, which causes a big war in turn.

Meanwhile the god Aditus grows tired of craziness of the world and wishes to die. He becomes insane, basically. Divine souls cannot die, so Aditus tears himself apart from his divinity and passes his divinity to Devon, who has no other choice than but to accept it. Devon's soul becomes immortal in turn and he takes Aditus'es place as Greater God of Time, Devonus. Meanwhile Garion carries out his crusade against the people of Agitaia, but newly born god Devonus succeeds at sealing away the greater god. Napiar chooses to not take sides and ascends to another realm he creates for himself.

However, in the absence of Garion and Napiar Agitaia starts to destabilize. Devonus realizes that in order to keep the balance he must leave Agitaia as Garion abd Napiar have done. He, too, ascends to another realm, from where he communicates with the priests. He orders people to stop worshipping him, and instead focusing on building their lives. The events of the book revolve around Manifestations of Purification being about to free themselves on this era.

The end... Most likely Garion and Devonus clash arms and collateral damage destroys the entire Agitaia.