Kudao has a massive category of supernatural demons, beasts, and yokai of many forms. But one thing they have in common is their roots, which all lead up to the father of all yokai; Mazoku, The God of Terror. Son of Umato and Otamum Mazoku has one purpose and one purpose only; to inflict and teach humanity fear, all in the name of balance, for the light cannot exist without the darkness. This demonic being is a living representation of the Kindao realm set in the Kudao realm, with similar origins to such as Rugong; his brother, who is the sole guardian against Mazoku's attack on the innocent. The Oni can shape-shift into infinite amounts of forms, but his true form is something above the limits of fear, described as a 7 eyed, 2 mouthed, 4 armed, horned devil, imprisoning damned souls within him for eternity, becoming stronger and more powerful with each screaming soul.

   Being one of the most feared megalomaniacal spiritual beings in Kudao, he is famed as a symbol of torment throughout Kudao culture. His symbolism is often used to discipline children into behaving or else "Mazoku will claim their souls". This has been proven false because Mazoku devours humans of all ages! But when he's not devouring humanity, he's manipulating them. Thousands of years ago, before Kudao was infested with yokai, Mazoku got bored and shapeshifted into a human, and tried to disguise himself with the village folk. This lead to him starting families with numerous women over the course of a few centuries, and the offspring given birth were hideous yokai/human hybrids, such as oni and kitsune. These creatures were banished from society and left to reside in the northern mountains of Tekkan, spawning more and more yokai, until they were no longer considered myths but pests.

   Even before Yamamura, Mazoku found a way to corrupt the mortal realm of Kudao with its counter realm of ghouls by deceiving the masses. Many gods have attempted to slay this sadist, some have even severed his head clean off, which was still not enough to kill him.