Oni

The Oni are a race of demons. They are the first evil to ever come into existence, as well as the creators of the three powerful Oni Masks. They inhabited the Realm of Oni and Dragons, the first realm in existence. It is unknown what the whereabouts of the majority of them are by the time of Season 9. They lived in Oni Land, a forbidden part of the Realm of Oni and Dragons.

History
Before the existence of any other realms, there was the Realm of the Oni and the Dragon. In this realm existed two races; the Oni and the Dragons. The Dragons had the power to create, while the Oni had the power to destroy, and so they waged a never ending war against each other. One day, however, a child was born, having both the powers of Destruction and Creation. When the Oni and the Dragons fought over which side the child should choose, the child left their world to start a new one, called "Ninjago."

Soon afterwards however, some of the Oni pursued the child to his new realm of existence, creating a temple deep within Primeval's Eye, where they depicted their origins on the walls of the temple. They would also seal away the Oni Mask of Hatred within the temple, which could only be taken by a being with Oni blood.

Thousands of years later, in the present, the majority of the Oni have disappeared and it is unknown what happened to them. A city of the Oni was found in disrepair, having been abandoned for centuries. The only full-blooded Oni that was known to be alive is Mistaké, who lived in Ninjago shapeshifted into human form.

Lloyd has said that the Oni is the darkness that Garmadon saw in the Departed Realm and they will come for Ninjago.

Known Oni

 * Mistaké (deceased)

Hybrids

 * First Spinjitzu Master (of Dragon descent)
 * Garmadon (of Dragon and human descent)
 * Lloyd Garmadon (of Dragon and human descent)
 * Wu (of Dragon and human descent)

Trivia

 * The Oni are based on Japanese folklore.
 * The Oni are the first evil to exist in the realms. However, because of Mistaké, it's known that not all Oni are evil.
 * This makes the Oni the first dark beings in the Sixteen Realms, predating The Overlord. However it is unknown if the Overlord has any links with the Oni, due to be the original evil of Ninjago, who rose from the shadows to balance out the First Spinjitzu Master's light.
 * According to a European Ninjago magazine, the Oni have mysteriously disappeared from the Realm of Oni and Dragons.
 * In "Two Lies, One Truth," it is revealed that there is a specific area of the Realm of Oni and Dragons that the Oni lived in.
 * Iron Baron and his Dragon Hunters have never seen an Oni, so they mistook the Ninja for Oni.
 * According to the Iron Baron, Oni are shapeshifters.
 * This was later confirmed in "Two Lies, One Truth," where Mistaké shows her powers.
 * It is unknown if in addition to her, there are more Oni in Ninjago.
 * It is also currently unknown what powers the Oni wields, apart from Destruction, as the First Spinjitzu Master acquired Destruction from his Oni heritage. However, as Garmadon was clearly terrified by the possibility of the Oni arriving to destroy Ninjago and feared them to the point that he was willing to be ruthless to his family to protect Ninjago from them, it is clear that if they are the threat Garmadon mentioned, the Oni hold immense power and their threat level may be the highest out of all the enemies the Ninja have ever faced. The fact that they seemed confident that they are capable of overpowering the First Spinjitzu Master, who is on the same level of power as the Overlord, who remains the most powerful evil, and forcing him to return to their realm further supports this. Also, as Garmadon stated that darkness will engulf Ninjago eternally if the Oni should arrive, it can be assumed that they also have immense power over darkness, which is not surprising as they are the first evil to exist, predating even the Overlord.
 * The Oni also seems to be extremely long-lived, as the First Spinjitzu Master, a half Oni, was able to live for several centuries and Mistake also did so. Even those very distantly related to the Oni seems to have that power, as Garmadon and Wu, who are technically only 1/4 Oni, was able to live for many centuries.
 * Lord Garmadon’s corrupted form resembles an Oni, but he lacks horns, does not have faun legs and has hair. This is because when he was corrupted, the Deverour's blood made his Oni side stronger so when he was struck by lightning, it brought out his Oni side on his appearance.
 * Garmadon mentioned that a darkness would soon consume all of Ninjago. At the end of "Green Destiny," Lloyd concluded that it was the missing Oni who would be the darkness.
 * If Lloyd is correct, this could mean that all the Oni are dead because Garmadon said he saw them in the Departed Realm. If they are dead, it's unknown how they died and it is also unknown how they will be revived.
 * Or perhaps he saw a vision of them. However, the former is most likely correct.
 * If Garmadon was being truthful and if Lloyd’s speculation is correct, then it seems that the Oni will be the antagonists in the Unknown Ninjago 2019 installment.
 * In the Croatian language, the word they translates to oni which adds to the theory that Garmadon was referring to the Oni at the end of "Green Destiny".

Gallery
Oni