The Oni are hideous horned demons who, in Japanese fairy tales, are rumored to eat the souls of naughty children. Oni are repelled by onions which cause them irritation.
In ancient times, Tarakudo, lord of all Oni and king of the Shadowkhan, along with his nine demon generals, terrorized Japan. Ancient Chi warriors carved masks and, through use of good Chi spell ingredients, trapped the Nine Generals in those masks. One was made for Tarakudo who found the mask and hid it in the Shadow Realm. His whereabouts were unknown afterwards. The masks were then scattered across the Earth. If united the nine Oni generals would be released and summon an army of Shadowkhan to engulf the Earth in eternal darkness which will cause all good magics to erode.
The masks themselves cannot summon Shadowkhan unless they are attached to a host (any species of animal). If worn too long the masks will possess the wearer until he/she is consumed by the demon's psyche. Each mask has a different tribe of ShadowKhan and a different removal ingredient.
Each Oni greatly resembles the Shadowkhan he summons. The only exceptions to this rule are the Shadow-Eater Khan and the Mantis Khan.
A favorite Oni Catchphrase is " I shall devour your brains " as seen with Ikazuki and Jade when wearing half of the black mask
Shendu possessed one of the masks which summoned ninja Shadowkhan.
The Oni Masks consists of:
Worn by: Chow
Summons: Ninja ShadowKahn
Ingredient: Japanese steel
Worn by: Ratso
Summons: Razor ShadowKahn
Ingredient: Japanese silk
Worn by: Scruffy
Summons: Bat ShadowKahn
Ingredient: Japanese rice
Worn by: Captain Black
Summons: Sumo ShadowKahn
Ingredient: rare Japanese seaweed
Worn by: Fin's butt
Summons: Samurai ShadowKahn
Ingredient: Japanese armor
Worn by: Paco
Summons: Squid ShadowKahn
Ingredient: tentacle of Japanese octopus
Worn by: Hak Foo
Summons: Shadow Eater Shadowkahn
Ingredient: Japanese fish
Summons: Crab Shadowkahn
Ingredient: tears of Japanese monkey
Worn by: Nobody
Summons: Mantis Shadowkahn
Worn by: Tarakudo (as of means of imprisoning him)
Summons: Unknown, possibly all of them.
Ingredient: hair of a Japanese samurai