Teacher of the year Ratsu.
Due to the loss of his love, he gives his life to the dark god in order to have the power to bring her back.
After many years of dealing with the agony from the darkness in his body he became stable and ruled over many countries as the Dark Lord Ratsu.
Over years he changed how he appeared but his power remained the same.
Through all his time he still kept his human heart. yet after many years as over lord, he was eventually overthrown by the forces of light. During his last moments he gave in and allowed the darkness to take him over completely ascending past that of a normal human, he became a God of darkness.
During his years as god, he eventually took off his mask of chains that held in his human heart and once again was able to become human again. It only on the inside.
When he finally saw what an animal he had become, he was disgusted and decided to go into exile.
During his exile he came across a town who's high priest knew what he was. After convincing the town to go against him they sealed his body changing his human form to what he truly appeared as on the inside.
During his imprisonment he was powerless, he was hated, he was feared for no reason, eventually his anger lead him to unleash all of his inner power and evolve into his newest form.
At last his power was at its peak and he was the true god of darkness again.