Ultra Dragon

"Someday he will be yours," Nya to Lloyd in Pirates vs. Ninja

The Ultra Dragon is a powerful combination of all the Dragons when they have reached adulthood. The four dragons went to the Spirit Coves to mature, and when their transformation was complete, they were combined into one large entity. The Ultra Dragon is given to Lloyd as a mount.

History
The Ninja's Four Dragons had not been seen since Snakebit when they left to grow up. Cole missed Rocky the most. They return, fused into one adult dragon (known as the Ultra Dragon) in The Day of The Great Devourer much to Cole's pleasure. Considerably more powerful in its adult form, the Ultra Dragon is able to strike the Great Devourer down. The Great Devourer recovers from the dragon's attack and retaliates, taking the Dragon out of the air.

The Ultra Dragon is later seen alive and well swooping in to rescue Jay and Zane from being consumed by the Great Devourer, giving Lord Garmadon an opening for it's weak spot, and a potential opportunity to destroy the Devourer. In the episode "Pirates vs Ninjas" Dareth was captured by Pirates and when he was forced to walk the plank he jumped, landing on the Ultra Dragon and he thought he had summoned it.