For eons, a mighty Evil Dragon was bound to the Underworld. Its head, having escaped its seal, emerged on Earth as an X-Soul through the help of a certain individual, and stole King III Gundam's power. Then, reviving its body at the bottom of the underworld, it began to move, seeking to rule both the surface and the underworld.
Boasting a colossal body comparable to a machine soldier, it overwhelmed the Britis Army, but was ultimately destroyed by a powerful blow from Legend Vatras SS.