| Spoiler warning!|
This article contains plot details and spoilers for a current or future season.
|“His throne. I already hate him.”|
|— Kai, referring to Iron Baron's throne.|
The Ultra Dragon was a powerful creature, formed when the Ninjas' dragons merged together while molting to adulthood. After this, the Ultra Dragon set off in search of the Ninja, finding them in Ninjago City during their battle with the Great Devourer. The massive dragon fought against the colossal snake, eventually helping the Ninja to immobilize the beast and allow Garmadon to destroy it.
The Ultra Dragon aided the Ninja in multiple conflicts, including their fights with their clones, Soto's crew, and the Ninjaball Run event. When the Ninja journeyed to the Dark Island, the Ultra Dragon remained in Ninjago to protect the citizens. Following this, the dragon was present in Ninjago City during Lloyd's climactic battle with the Overlord.
After the Overlord's defeat, the Ultra Dragon returned to his birthplace, the Realm of Oni and Dragons. Some time later, it somehow met its end. The Dragon Hunters use its skeleton as a throne for the leader, the Iron Baron.
Shortly after the Ninja claimed the Destiny's Bounty as their new home, their dragons began to molt, which Master Wu explained was a prelude to their final maturation. The Ninja were forced to release their dragons so they could travel to the Spirit Coves and complete their transformation.
During their molt, the four dragons merged into a single large entity. After this change, the new Ultra Dragon left the Spirit Coves and began searching for its masters. It arrived in Ninjago City just in time to save Nya and Lloyd from being consumed by the Great Devourer. Using all four elemental powers, the Ultra Dragon seemingly forced the Great Devourer into retreat, only to be knocked out of the air when the Devourer ambushed it from underground.
The Ultra Dragon recovered from his injuries in time to take part in the Ninja's plan to immobilize the Great Devourer. As Jay and Zane slid off of an ice slide created by the latter, the Ultra Dragon swooped by and caught them before they could fall or be consumed by the Great Devourer. As the Ultra Dragon landed on a nearby building, the Ninja dismounted to see that the Devourer had become stuck, giving Lord Garmadon the chance he needed to attack its weak spot and destroy the serpent.
When the Ninja moved into the Hero Suite, the Ultra Dragon stayed in the built-in dragon keep on the roof where it rested, still recovering from the injuries inflicted by the Devourer.
Nya gave Lloyd a short dragon lesson while she was feeding the Ultra Dragon his medicine, informing him that while the four elemental dragons belonged to the four Ninja, the Ultra Dragon belonged to him. Strengthened already, the Ultra Dragon then took off from its resting spot atop a building to go stretch its wings.
The Ultra Dragon flew over the Endless Ocean where he came upon the Black Bounty, manned by Lord Garmadon and the Serpentine. The dark ship pursued the Ultra Dragon over the ocean, but he escaped without injury due to Garmadon not realizing that his new Mega Weapon could only be used to create, not destroy.
The Ninja rode the Ultra Dragon to Darkley's Boarding School for Bad Boys when Lloyd received an invitation from his former classmates to a party in his honor. Brad Tudabone was suitably impressed when he saw Lloyd's new means of transport. After overturning the students' plot to turn Lloyd evil and fighting off the Bizarro Ninja, Cole rode the Ultra Dragon home while the other four Ninja rode in the Ultra Sonic Raider.
Lloyd enters the Ninjaball Run with the Ultra Dragon as his transport. He accidentally rammed the Black Bounty during the desert portion of the race, ruining Lord Garmadon's attempt to attack the Ninja. In the Glacier Barrens, Lloyd uses the Ultra Dragon to spot a shortcut for the Ninja's use, only to be knocked out of the race by Kruncha and Nuckal's Skull Truck (although it also caused the Skulkin vehicle to crash). The Ultra Dragon eventually recovered and returned to Ninjago City, where he helped Lloyd reclaim the Black Bounty from Lord Garmadon.
When Wu mentioned that the Ultra Dragon made a mess, the Ninja fool Lloyd into cleaning it up, and told him the responsibilities of having a pet before Nya arrives, telling them about a situation at the museum before Lloyd hands her the bag, and she wonders what it is before discovering it is the Ultra Dragon's excrement.
The Ultra Dragon escaped the Overlord's attack on Ninjago City and flew to the Island of Darkness, where he gave the Ninja, Master Wu, Misako, and Dr. Julien a ride back to Ninjago. He took part in the assault on the Overlord's fortress, being piloted by Master Wu when the Ninja jumped off to aid Lloyd in fighting the Stone Army, but was eventually taken out of the fight when Nya—corrupted by Dark Matter—hit him with a shot from a turret on the tower. The Ultra Dragon recovered in time to reunite with the Ninja after Lloyd defeated the Overlord.
At some point after the final battle between Lloyd and the Overlord, the Ultra Dragon returned to the Realm of Oni and Dragons. Unfortunately, it was later killed by the Dragon Hunters, who now use its skeletal remains as a throne for the Iron Baron.
While held captive, Kai notices the Iron Baron's throne is made from the remains of the Ultra Dragon and declares he already hates the Baron for his actions.
The Ultra Dragon appears as a large white Dragon with a black underside. He has four heads with long necks, each corresponding to one of the elemental dragons that formed it. The colored markings on each head indicate its former element; from the dragon's left side, they are Fire, Ice, Earth, and Lightning.
The Ultra Dragon has two large wings with three orange claws at the main joints. Small green spines are visible above the wing claws and on its tail. It is also usually seen with a seat and a set of reins on its back, allowing the Ninja or their allies to control its flight.
Powers and Abilities
The Ultra Dragon is a powerful flyer, able to carry the Samurai Mech with ease. He can use his multiple claws, spines, and fanged mouths for melee combat, and has access to the elemental abilities of his four component dragons:
- Earth: Increases his striking power.
- Fire: Allows him to spit fireballs or breath streams of flame.
- Ice: Enables him to freeze things with his breath.
- Lightning: Can be discharged as damaging bolts from his jaws and talons.
- Apart from the Earth Dragon's head, all four of the Ultra Dragon's heads are identical save for color.
- The Ultra Dragon's overall body form is most similar to the Lightning Dragon (four legs and two large wings). Ironically, the Lightning Dragon's head is the only one of the four to have markings in a different color from its original scale color (presumably to avoid confusion with the Ice Dragon's markings).
- Zane compares the dragons' metamorphosis into the Ultra Dragon to the Ninja unlocking their True Potential.
- The Ultra Dragon appears in LEGO Ninjago: Shadow of Ronin, depicted as Lloyd's dragon.
- Tommy Andreasen has said he believed the Ultra Dragon returned to the Spirit Coves. However, it's later revealed it returned to its true home world and met its fate there, so this idea had likely changed at some point when Season 9 was being conceptualized.
- According to the Hageman Brothers, the Ultra Dragon was killed by the Dragon Hunters with its skeletal remains being used as Iron Baron's throne.
- The Ninja did not recognize the throne as the Ultra Dragon's remains, and never discovered this before going back to Ninjago or before Season 9 ended. 
- ↑ https://twitter.com/brothershageman/status/1015443676074426368
- ↑ https://twitter.com/TommyAndreasen/status/790868102946951169
- ↑ https://twitter.com/brothershageman/status/1015501526456913920