In the days of old, a great cataclysm occurred that plunged the world into ruin. Countless lives were lost as the people struggled to stand against the oncoming disaster. Its energies all but spent, humanity's hope seemed lost when a pair of siblings appeared. This brother and sister together fought the calamity, and saved the world from annihilation. The sister they called Child of the Full Moon. After the struggle, she remained with the earth. Her brother they called Brave Vesperia, and he ascended to the skies to watch over the world.
Goddess who bathes this world in her golden light, you are named Child of the Full Moon. Your brother, Brave Vesperia, watches over us from the skies. You remain bound to your mother, the earth, and will shelter her with your unceasing protection.
...The leaders of the ancients possessed an innate power, and were called the Children of the Full Moon. The Shrine of Zaude received their lives and power. It sealed the Adephagos away, saving the world. As humans had brought forth the Adephagos, human lives were used to seal it again. The remaining Children of the Full Moon, with the Entelexeia, decided how the world would be. The Imperial Family are their decedents, and thus Dein Nomos—the key to Zaude—will prove a true emperor. As well as being the key to Zaude, Dein Nomos is one of the few ways to calm—kill—an out of control Child of the Full Moon. The agreement between the Children of the Full Moon and the Entelexeia was to bury most of the Blastia, and the Children would watch over the rest. Before long, the role of supervisor turned to one of absolute authority. The Empire was born two hundred years after the Adephagos was sealed away.
The Entelexeia occasionally refer to Children of the Full Moon as a "poison". This is because a Child draws more aer than any blastia - and thus is a threat far greater than any blastia. Any blastia causes an Aer Krene to produce more aer, and a Child of the Full Moon causes the Krene to produce at a greater rate. This has at least one Aer Krene to run rampant, turning the surrounding area into a desert.
The Kritya. Stewards of wisdom, founders of the mighty Geraios, and ancient sages. Their misbegotten wisdom has sown only the seeds of ruin. The blastia they created granted them blessings, but also blighted the aer, lifeblood of this world. The blight grew ever stronger and brought forth a cataclysm... In their terror, they gave a name to the cataclysm: the Adephagos. The world united to challenge the Adephagos, and banish the loathsome power which created it. The Geraios civilization was lost, the Adephagos was quelled in the end. Hearing the world's prayers, life faded from the Child of the Full Moon. The Adephagos disappeared into the void.
I might update this later, but this is most of the information