Kur

"It is madness for sheep to talk peace with a wolf."

Hectic Dragon Emperor Kur (猛竜帝・クアル, Mōryūtei Kuaru), more commonly known as the First Dragon of Insanity (茫発狂の初代竜, Mōhakkyō no Shodairyū lit. Founding Dragon of Infinite Madness), was a Dragon that descended into madness and became a true monster that would destroy anything that dared to stand within its path. Originally, Kur was a Dragon General (竜の将軍, Ryū no Shogun), a special rank that was granted by the Dragon King to show one's power. Kur himself was known for possessing immense strength as it was said that his potential could allow him to be the next in line to become Dragon King. However during the great Dragon Civil War, Kur had began to question why he served alongside his fellow Dragon, believing that he was clearly capable of annihilating anything that stood in his way with no trouble. This thought process eventually led to Kur descending into madness with his final push hearing the words of a mysterious human who convinced him to show both humans and dragons that he was their rightful ruler and that he should send into a state of destruction. It was because of this that Dragons that were originally fighting against each other, set their differences aside and attacked Kur along with their Dragon Slayer that they had taught their magic too. After many years of fighting and death, the combined forces were able to kill Kur and send his corpse below the earth, to be forgotten.

Trivia

 * In Sumerian mythology, Kur is considered the first ever dragon, and usually referred to the Zagros mountains to the east of Sumer.