Tenkai Dragon

The Tenkai Dragon (Japanese: 天界のドラゴン, Tenkai no Doragon) is a powerful creature that lived on Quarton. It was summoned by Vilius to combat the Corekai. Unfortunately, it proved too powerful, and he lost control. It was later defeated by the Tenkai Knights, who caused it to shatter into the five Dragon Cubes, which were scattered across Quarton.

Reviving the Tenkai Dragon
In the order to awaken the Tenkai Dragon, the five Dragon Cubes must be combined, and one of the two keys must be used to unlock either the Dragon's good side or it's evil side. The Tenkai Knights managed to find the White Key and unlock the Tenkai Dragon. However, it was captured by Dromus for Vilius.

In "A New Knight", the Tenkai Dragon was commanded to attack the Knights by Vilius until he was knocked off of the Dragon by Dromus. The Dragon was then trapped by the Guardians and Bravenwolf used the White Key to change it from evil to good. He and Dromus used the two keys power, causing the Dragon to split into Dragon Cubes. They went into their respective Knight, unlocking Phoenix Mode.

In "Vilius Returns", Vilius took the Tenkai Knights energy to reawaken the Dark Tenkai Dragon, without using the black key. Because of this, the Dragon was unstable. When Dromus came from the sky and attacked the Dragon, it split into black and white Dragon Cubes. The white cubes went into the Tenkai Knights and the black cubes went into Vilius, giving them elemental powers.