Rudolph is the leader of the Investiture Beings.
When it came to the war between Rosekstan and Nirvana's White Brigade, Rudolph fired a laser from the floating city which petrified Michael where he stood. It even rose a giant wall which also petrified any soldier on both the Rosekstan and White Brigade sides as they were shown petrified on the wall.
He later has his encounter with Shu where they had their first fight. Afterwards, he unleashed his dragonoid-like creatures upon the city Shu, Bouquet, Marumaro, and Noi were staying at. After they destroyed the creatures, Rudolph got away.
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 Brigade and Shu's group.
Following Fagino's destruction, Rudolph then had Rottarace fight Hildegard after what she did in her encounter with Noi in the underground ruins. When Shu rescued Lota, he then engaged Rudolph. Rudolph later transformed his castle into a war machine in his final act upon the world. The Shu/Blue Dragon then fought Rudolph which led to the point where their breath attacks collided. Though the Shu/Blue Dragon fell towards the ground, Rudolph then began to crack and fell toward his war machine where he exploded.
Rudolph's true form is a four-winged gold dragon with a maced tail and can even bring it out in Shadow form.Rudolph is extremely powerful being respect by even the other heaveanly dragons and is no doubt probably the most strongest character shown in the blue dragon series alone,and is strong enough to combat even blue dragon in his shu/blue dragon merged form and was still able to hurt blue dragon in their final clash despite being defeated in the end also.In dragon form, he is shown to have the abilities to duplicate and become intangible in combat. He also possesses legendary raw strength.