Realm of Oni and Dragons

The Realm of Oni and Dragons is one of the Sixteen Realms parallel to Ninjago that appeared briefly in Season 8 and is a main setting of Season 9. It appears to be a sandy place, and was the very first realm in existence. It is where the First Spinjitzu Master originated from, before he fled to create Ninjago.

Distant Past
The first of all of the Sixteen Realms, in this world there lived two species of beings: the Oni and the Dragons. The Dragons had power over creation, and the Oni had power over destruction. Effectively being polar opposites, a seemingly never-ending conflict between the two kinds was sparked that would go on for ages. One day, a child with the powers of both sides was born, who understood the necessity of the roles both the Oni and Dragons played in the balance. But instead of ending the war, they simply fought for control over him in order to win their sides of the battle. Torn between both worlds, the child abandoned his home to start anew. The child went on to become the First Spinjitzu Master, and with his powers, he created the world of Ninjago.

Big Trouble, Little Ninjago
After using Traveler's Tea given to them by Mistaké, Kai, Jay, Zane, Cole, and Toddler Wu end up in a sandy place, their Ninja uniforms ruined and part of the Destiny's Bounty behind them. When they look over their surroundings, they see dragons and realized they have been transported to the First Realm.

Inhabitants

 * Oni
 * Mistaké (formerly)
 * Dragons
 * Firstbourne (Mother of All Dragons)
 * Ultra Dragon (Before getting killed by Iron Baron)
 * Dragon Hunters
 * Iron Baron (leader)
 * Heavy Metal (second-in-command, formerly)
 * Jet Jack (second-in-command)
 * First Spinjitzu Master (formerly)

Outsiders

 * Kai
 * Cole
 * Zane
 * Jay
 * Wu

Notable Locations

 * Oni Land
 * Dead's End
 * The Pit

Legend
"Long before time had a name, there was the Realm of the Oni and the Dragon; the Dragon had the power to create, the Oni had the power to destroy. Their war was never-ending. But a child arrived, born of both worlds. The child understood the power of both: without one you could not have the other. But when the Oni and the Dragon fought over which side the child should choose, the child abandoned their world to start a new one called "Ninjago." After the First Spinjitzu Master created Ninjago, he fathered two sons of his own. He thought he could escape the war. He saw the evil of the Oni was awakened to be unleashed in one of his sons—Lord Garmadon! It was up to Master Wu to control his brother's undying thirst to destroy, and with some help, Lord Garmadon was destroyed by the most powerful force of all—the love of his own son." —Mistake

Season 8: Sons of Garmadon

 * 77. "The Oni and the Dragon" (pictured)
 * 84. "Big Trouble, Little Ninjago"

Season 9: Hunted

 * 85. "Firstbourne"
 * 86. "Iron & Stone"
 * 87. "Radio Free Ninjago"
 * 88. "How to Build a Dragon"
 * 89. "The Gilded Path"

Trivia

 * This realm is the homeland of the First Spinjitzu Master, a being born of both Oni and Dragon.
 * It is also home to the Firstbourne, the mother of all Dragons, and possessor of every Elemental Power that her children possess.
 * The Oni also live here, at least, they used to. According to a German magazine, they have mysteriously disappeared from the realm.
 * It also seems that the realm was divided into Oni land and Dragon land.