Human Devil was Chaber Mike, and his Chinese name was Xia Lixing. He was one of the few guys back then whom the Old Devil had been able to defeat only by a narrow margin, but it wasn't the Old Devil who killed him. Only now did the Old Devil learn, from the profile in General Bai's hands, how Xia Lixing had died.
"Xia Lixing was killed in the bombing of Divine Rank Island," General Bai said. After listening to the Old Devil's account, he connected all the dots.
After fighting the Old Devil back then, Human Devil Xia Lixing had been seriously wounded, and he fled to Divine Rank Island, known as a Soul Formation paradise, to cultivate. He was then discovered by the International Alliance of Cultivators, who promptly decided to take him down completely at the cost of destroying Divine Rank Island.
In the end, Xia Lixing was killed when the International Alliance of Cultivators bombed Divine Rank Island.