The Elemental Dragons are mystical creatures that belong to both Ninjago and The Underworld, and ferry between them. They were the Guardians of the four Golden Weapons and are generally not vicious unless the Weapons are threatened. They debut Masters of Spinjitzu
Ninjago has four known Dragons: The Fire Dragon, the Lightning Dragon, the Ice Dragon, and the Earth Dragon.Sensei Wu placed each Dragon to guard one of the Golden Weapons, each in tune with its elemental properties. In Masters of Spinjiztu wrttten by trachie17 Seamus and Tracy both have Elemental Dragons of their own one is the Metal Dragon owned by Tracy and the Spirit Dragon owned by Seamus Finnigan
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 alone.
After their respective time away from the Ninja, the Dragons morphed into the Ultra Dragon. It appeared during the fight against the Great Devourer and nearly defeated the creature. It is now Lloyd's form of transportation. He used in it in Ninjaball Run.
In Mystery Case Files: A Thanksgiving Mystery and Masters of Spinjitzu there roles are the same as the show except there are more owned by the alternate version of the girls kids and the current Tracy and Seamus.
In Masters of Spinjitzu their roles are the same except there are two more dragons one for Tracy a Metal dragon, which she dubbed Silver and the other is a Spirit Dragon which its owned by Seamus and dubbed Spirit.
Though joked by Emmy in the one shot Family is Family written by trachie17 it is unknown if there is a place for Silver and Spirit at HQ however this will be confirmed in the upcoming story MCF and the Return of Pythor.