Fire and Ice series
The Furian and Frial have maintained peace for millennia, though they are opposites. The Frilan worship Magmon, god of fire and passion. Their lands stretch from the southern volcanic ring to the temperate north. They are ruled by a royal family. The Frial worship the goddess Frilan, a goddess of ice. Predictably, their lands stretch from the polar north to the temperate zone. They are ruled by a god vessel called the Ician. They are as different as can be.
Once every cen-centenial, the alliance is renegotiated and a celebration ensues. There's just one little thing that has to happen first. The Ician is reborn for her people every generation. The He-Atal, Magmon's god vessel, only appears for the cen-centenial. He is conceived at Magmon's celebration, born in the Dragon God's fire, consumed by His hunger, taken into the temple to be trained to survive the burn... And finally, he is presented to the Ician with one job and one job only: seduce a frigid woman.