Technology & Combat Characteristics
Physically, the Grand Master Gundam appeared as a combination of the Four Heavenly Kings, which included the upper body of GF13-001NHII Master Gundam, the body and horns of Grand Gundam (in quadruped mode), the wings and claws of Gundam Heaven's Sword, and a much larger version of the Walter Gundam as its tail. The majority of the behemoth was colored black, with the Gundam Heaven's Sword's feathers and talons, the Grand Gundam's cannons and horns, and both the Walter Gundam and Master Gundam components being the only parts in their original colors. The entire machine is also suffused with green tentacles/cables, similar to most of the Devil Gundam's spawns.
Being infested with DG Cells, the Grand Master Gundam could regenerate from astonishing amounts of damage and reshape its form at will. While attempting to recover from the Erupting Shuffle Alliance Attack, it transformed Master Gundam's left arm into a powerful beam cannon and manifested large masses of tendrils to bind the Shuffle Alliance's members.
History
During the 13th Gundam Fight, the JDG-00X Devil Gundam created the powerful Four Heavenly Kings for its own defense. By the time the Gundam Fight ended, all four kings had been destroyed, but Ulube Ishikawa had resurrected the Devil Gundam in space (with the unwilling Rain Mikamura as its core). Now back to its full strength, the Devil Gundam merged with the Neo-Japan space colony, feeding off of the colony's generator as a power source as it prepared to consume and destroy the Earth. When the Shuffle Alliance entered the colony to destroy the generator, Ulube had the generator transformed into the Grand Master Gundam and prepared to pilot it against his foes.
The Grand Master Gundam intercepted the Shuffle Alliance, proving too strong for any of them to defeat. One by one, the members of the Shuffle Alliance were disabled: Chibodee Crocket's Gundam Maxter had his own Bursting Machine Gun Punch turned against him before being pinned under the Grand Master Gundam's foot; George de Sand's Gundam Rose was impaled by the Grand Gundam's horns; Sai Saici's Dragon Gundam was caught in the jaws of the Walter Gundam's head; Argo Gulskii found his Bolt Gundam seized by the talons of Gundam Heaven's Sword; finally, Domon Kasshu's God Gundam was overcome by the Master Gundam's Sekiha Tenkyoken.
As Ulube gloated to his pinned foes, he revealed that he had been completely assimilated by DG Cells, reducing him to an avatar for the Devil Gundam itself. However, Domon regained his will to fight after being encouraged by his friends, allowing all five of the warriors to unleash their Hyper Modes and free themselves from their respective bonds. By combining their Hyper Modes, the Shuffle Alliance was able to defeat the Grand Master Gundam, seemingly shutting down the Devil Gundam.
However, after Domon left to seek out Rain and the Devil Gundam's core, the Grand Master Gundam began to regenerate – the Colony Devil Gundam had evolved to the point where it could even repair a component as vital as its main generator. The remaining four Shuffle Alliance members were forced to battle the partially-restored Grand Master Gundam, eventually defeating it for good as Domon freed Rain and eliminated the Devil Gundam's core.