Dragons

Dragons are mystical creatures that originated from the Realm of Oni and Dragons, the first realm in existence. The legendary beings are in tune with Elemental properties, having originally been masters of Creation. They are said to be connected to both Ninjago and the Underworld, enabling them to travel between the two worlds at will.

Master Wu once tasked four Dragons linked to each of the four Elements to guard the four Golden Weapons, and they were generally not vicious unless the Weapons are threatened.

Known Types of Dragons
There are eleven known types of Dragons: Many others
 * Ultra Dragon (Deceased)
 * Fire Dragon
 * Lightning Dragon
 * Ice Dragon
 * Earth Dragon
 * Nindroid MechDragon
 * YinYang Dragon
 * Light Dragon
 * Shadow Dragon
 * Wind Dragon
 * Ghost Dragons

Known Dragons

 * Firstbourne (The Mother of All Dragons)
 * The Overlord
 * Ultra Dragon (Lloyd's Ultra Dragon; deceased)
 * "Flame" (Kai's Fire Dragon)
 * "Wisp" (Jay's Lightning Dragon)
 * "Shard" (Zane's Ice Dragon)
 * "Rocky" (Cole's Earth Dragon)
 * Bandit (YinYang Dragon)
 * Stormbringer (Lightning Dragon)
 * Stormbringer's Baby (Lightning Dragon)
 * Slab (Earth Dragon)
 * Wind Dragon
 * Fire Dragon
 * Ice Dragon

Hybrids

 * First Spinjitzu Master (of Oni descent; deceased)
 * Garmadon (of Oni and human descent)
 * Lloyd Garmadon (of Oni and human descent)
 * Wu (of Oni and human descent)

History
The Dragons seen in Ninjago were descended from the Dragons of the Realm of Oni and Dragons. The Firstbourne Dragon had all Elemental Powers except Destruction and Darkness, and her offsprings constantly waged war against their arch enemies, the Oni (who were beings of Destruction, the polar opposite of Creation). When a child was born, the two sides fought over him until he left the realm. The child also struck a friendship with the Firstbourne when he tried to stop the war.

Later, that same child would grow up to empower a group of humans with the powers he gained from the Dragons, the Elemental Masters.

Master Wu placed each Dragon to guard one of the Golden Weapons, each in tune with its elemental properties. The dragons guarded the weapons for many years, until an increase in Skulkin activity led Master Wu to believe that the weapons had to be retrieved before they could fall into Lord Garmadon's hands.

The four Ninja had to avoid each of the Dragons as they recovered the four Golden Weapons. When the Weapons were stolen by Garmadon, they discovered that the Dragons only wanted to protect the Weapons, and would gladly aid the Ninja in their quest. Afterwards, each Ninja kept the Dragon matching their elemental properties as a pet, in addition to using them for transportation. This allowed the Dragons to continue guarding the Weapons, as the four Ninja wielded them in defense of Ninjago. As Jay decided to visit his parents, all four Dragons were molting and had to leave the Ninja. The Ninja had to go on the journey to Ed & Edna's Scrap N Junk on foot.

During their time in the Spirit Coves, the Dragons morphed into the Ultra Dragon. It appeared during the fight against the the Great Devourer and nearly defeated the creature. It briefly served as Lloyd's personal transportation until he mastered the Golden Dragon, most notably in "Ninjaball Run."

When the Overlord possessed Garmadon's body in "Return of the Overlord," he appeared as a humanoid dragon. As his power continued to increase in the following episode, he mutated into a full Dragon.

During "Lessons for a Master," Firstbourne gave the Marooned Ninja Dragons that correspond to their elemental powers. They use them to get out of the First Realm and into Ninjago. They also use the dragons during "Green Destiny", where the dragons save the ninja's allies from the Sons of Garmadon and used them against the Colossus.