Rudolph is one of the Investiture Beings introduced in Blue Dragon: Trial of the Seven Shadows. He is the leader and head chairman of the Dragon Council and the final antagonist until his eventual demise.
Personality
He's been shown to be calm and collected as Rottarace being the chairman and high magistrate of all decisions. He remains composed under the intense situations and deals with rising issues that are unexpected or which opposes their laws, and will not hesitate to deliver the judgment even if their own kin are responsible, such as Mikhail's impatience actions and Rotta's treason. He stands firm to all decisions before finalized and tends to brush off any point of reason which stands in the way, as shown when he ignores Noi's attempts for negotiation.
He remained secretive and critical as the series progresses, Rudolph reveals himself as a ruthless dictator who uses the trials to collect data to bring humanity to extinction. After Hildegard decided to remain neutral during the final battle, Rudolph still remained his calm demeanor as long as everything abides by his rules.
History
Rudolph remained still as he monitors the trials conduct by the other Investiture Beings. As the war between Rosekstan and the White Guardians began, Rudolph watched as the conflict escalated despite Shu's progress to neutralize both parties and Mikhael's interfering on his own accord. Rudolph finally took action where he fired a laser from Castle Azure, which created a wall dividing both sides and petrifying anything in its vicinity with Mikhael in the center as punishment for his actions.
Rudolph finally appeared before Shu to deliver his final trial. They fought not before Rudolph unleashed his wyvern army upon the city, but were destroyed by Shu's party. In the next encounter, he appeared before Shu's group announcing their decision to eliminate mankind, but was held back by Vermillion in his sacrificial attempt for Shu's group accompanied by Primella and General Szabo to escape.
Rudolph then had part of the wall destroyed during the Investiture Beings' invasion. He managed to fight Shu again while Noi, Bouquet, and Marumaro were off doing their own missions. When it came to Hildegard and Fagino's fight with Shu and the White Brigade at Z'Mey, Rudolph awakened Amethyst Dragon, Blizzard Dragon, Moody Dragon, Phantom Dragon, and Spark Dragon to eliminate the White Guardians and Shu's group.
Following Fagino's destruction, Rudolph then placed Rottarace on trial for treason against her encounter with Noi in the Laibaha Ruins. After Shu rescued her, Rudolph revealed his ulterior motive to destroy humanity and that all the trials were rigged from the beginning to collect data. This included Fagino's death to test Blue Dragon's true awakening. As the final battle escalated with Noi's awakening to stall time for Shu to recover, Rudolph later transformed into his final form where he merged with Castle Azure and transforming it into a war machine. All seems lost until Rosekstan catches up thanks to Loki's tracking device on Shu pinpointing their location. Jiro, Kluke, Delphinium and Loki join the assault until Blue Dragon clashes one last time where their breath attacks collided. Though Shu finally became exhausted and fell towards the ground, Shu remained victorious as Rudolph's body cracked until his destruction and the castle exploding.
Abilities
Rudolph is considered the extremely powerful character even outside dragon form. All the other dragon council members respect his immense strength and overwhelming power. Rudolph's unique ability is being the only dragon with a fourth form that outclasses all dragons. To merge with their sky castle fortress which can transform into a massive skeletal dragon with extremely high levels of power enough to destroy 75% of Rosekstan's air fleet.
Dragon Form
Rudolph's true form is a muscular four-winged gold dragon with a maced tail and can even bring it out in Shadow form. He remained the most powerful character who even manages to best a fully materialized Blue Dragon despite Shu leveling the odds in terms of raw strength. In dragon form, he is shown to have the abilities to duplicate and become intangible in combat.