The wisest dragons contend that the world was born in battle. According to myth, the emptiness before creation was the domain of three mighty dragons. Golden Siberys was the source of all magic. Gentle Eberron was the fountain of life. Cruel Khyber was the master of secret knowledge, and of the powers that lurk in the darkness. Together, they held dominion over the fate of all, and they pondered the proper shape of the universe.
In the beginning, the Progenitors worked together. They started with the thirteen planes, but as they molded reality, rifts began to form between them. Dark Khyber grew greedy, and noble Siberys responded by becoming more forceful; each sought greater influence in the work. Daanvi, Fernia, and Irian bear the prevailing mark of Siberys. Kythri, Mabar, and Xoriat show the dominant touch of Khyber. Eberron sought to mediate but could not bridge the divide.
When it came time to create the final, central plane, the tensions between Siberys and Khyber could not be contained. The dark one tore into her sibling, mortally wounding the gold dragon and scattering his scales across the sky. Although not powerful enough to defeat her, Eberron knew that Khyber could not be allowed to benefit from her deeds. The gentle one refused to fight Khyber with claw and tooth. Instead, Eberron embraced her, trapping Khyber within her smothering coils. Eberron called on the powers of life, giving birth to soil, tree, and ocean, and so transformed herself into a living prison that Khyber could never escape.
Thus Eberron became the world on which all life grew. To this day, she nurtures and sustains all. Siberys’s remains became the ring around the world; his scattered scales became the stars. Khyber remains trapped within—the Dragon Below, the Mother of Monsters, the source of all darkness—forever struggling to escape and bring an end to it all.
Source: Dragons of Eberron
