Alone

Hades, 冥王ハーデス / アローン

Arōn is an Italian painter who was previously known as Hades' incarnation. He grew up alongside Sasha and Tenma, both of whom later became his enemies. Despite being an orphan, Arōn has a pure soul and believes that everyone possesses good qualities. He disapproves of violence and feels that it is unnecessary to resort to such measures. Hades chose to reincarnate in Arōn's body because he believed that the young painter had the potential to be a powerful force for good. Initially, Arōn rejected his fate as the God of the Underworld, but was later convinced by Hypnos and sealed by Pandora's kiss. Before Tenma left for the Sanctuary, Arōn made a promise with him that they would both strive to become better versions of themselves - while Tenma tried to become a Saint of Athena, Arōn committed himself to becoming a skilled artist so that he could complete a painting of Tenma when they were reunited.

Spoilers:

It has been implied that Alone is not yet totally possessed by Hades as Alone drew in the Lost Canvas an image of Tenma, Sasha and himself in their childhood. After seeing this, Pandora uses a seal given by Hypnos and Thanatos to seal him in a dimensional isolation, in hope that he will continue painting the Lost Canvas without distractions, and to keep him away from the reaches of anyone from his childhood life. During the next two years, his personality makes a drastic change after seeing everything he painted dies. Convinced by Hypnos, he starts to believe that death is the ultimate salvation. And to bring salvation to the entire world, Alone starts to paint the Lost Canvas, a painting of the Earth viewed from space, so that after he finishes it, the entire world will die.