I'm still working out the kinks of my Ninja Gaiden/Dead or Alive upgrades and was kinda hoping to hold this off but I'll throw you guys a bone for now
From the Ninja Gaiden Book of Genesis:
In the beginning, the first deity Gurdu had form out of a great nothingness and began to give order and function to the universe. However unknown to Gurdu existed an instinctual fear in a remote territory of chaos. As time passed this fear grew and took shape, evolving into hatred. Hatred would keep growing until it reached the level of a Deity. Thus the evil god; Vigoor, came into being.
Vigoor, the ancestor of all Evil Deities, set the first conflict into motion as he started to devour the territories of Gurdu, beginning at its centre. Chaos enveloped the world while Vigoor reshaped it, causing endless solar and lunar eclipses to occur, as the primitive earth shook and split, and the seas dried up only to flood into existence again. Intense winds swept over everything as evil flames burned down all of existence ignoring even the concept of time itself.
In the chaos, Gurdu eventually lost strength and fell apart, breaking into quarters, each part becoming a new deity with Gurdu's characteristics of Sentiment, Wisdom, Creation and Immorality. These new Deities possessed little power as they were born into a panic state of being. However the Deity of Creation, Serpent, who had kept some semblance of sanity, gave birth to the seeds of life.
The seeds took root, maturing in the chaos to become the 13 dragons. Once fully grown, the Dragons waged a long, hard and fierce war against Vigoor that would span over the aeons, until Dragons finally defeated Vigoor. The world now found peace, watched over by the Dragons as the Deities descended from Gurdu reshaped the world. It was during this time the first spark of human life emerged in early human tribes.
Though Vigoor was defeated, he would manage to hold on to existence through the envy of the youngest Dragon. This allowed his influence to re-emerge over the ages in many forms, starting with the envy of the youngest Dragon, who would emerge as the Dark Dragon, bringing forth Vigoor's death and destruction of the world. Then in form of his spawn, the Evil Deities and Archfiends such as Vazdah who rose from Vigoor's corpse. These Evil Deities would spawn the Fiends who draw their strength from Vigoor. His influence finally emerges within the Holy Vigoor Emperor, the disciple of Vigoor who would later be infused with Vigoor's essence (the powers of all the evil deities) upon unsealing the Dark Dragon Blade.
Basically, Vigoor can split the earth apart, split it, dried up the seas then brought them back into existence, shook the entire earth, caused countless lunar and solar eclipses, could affect time and space themselves.
The 13 dragons were roughly on par with Vigoor and managed to defeat him before then reshaping the planet. Ryu also fought the youngest dragon in the DS game for what it's worth, and is afraid of using the True Dragon Sword in fear of it destroying the earth (it is equal to the Dark Dragon Blade which could consume the world with its darkness)
