In Legend of the Five Rings, Onnotangu is the male half of the first man and woman pair created by the Gods that Have No Names- the other half being the goddess Amaterasu. During the Naming of the world, he would think up a name, and Amaterasu would bestow it upon the formless thing.

When he saw how his wife had been lavishing her attention on the things that had been named rather than himself, he became jealous and began pursuing her across the sky. The naga, nezumi, kenku, and a myriad of other creatures flourished throughout these times, until one day when he caught her in the sky.

Nine months later, when she was giving birth to their children, the Kami, Onnotangu realized that a creature with the blood of both the Sun and Moon would be more powerful than himself, and as she gave birth to each one he devoured it. Each time he devoured it, though, Amaterasu offered him a cup of sake with a drop of poison. By the time she was done birthing Hantei, he was too stoned to notice that she had fed him a rock instead of a screaming newborn.

When Hantei returned to free his children from his father's belly, their battle rocked the heavens, and ended up with Onnotangu's son drawing all his children down to the world below. The tears of Amaterasu that fell mixed with his blood leaking from the heavens, and thus the first humans were born.

During the first thousand years of the rule of the Hantei dynasty, Onnotangu (more commonly called Lord Moon, as invoking his name was akin to asking for his attention) was worshiped as a wrathful deity that must not be tampered with- and those that did worship him were usually involved in some way or another with the Shadowlands.

The events that would follow the ascention of Toturi to the throne, however, would eventually spell his doom. When Mirumoto Hitomi recovered the artifacts that had fallen to earth with the Kami- his blood (the Obsidian Mirror), his hand (the Obsidian Hand), and his bones the Obsidian Sword, she would ride a ki-rin to the heavens and do battle with him, eventually destroying Lord Moon and assuming his place as the Moon in the Celestial Heavens.