Pluto

Plutos are demons that have undertaken and survived the Hell's Pilgrimage, which requires the demon to survive a battle with each of the four Archangels and the four Archdevils. Many demons who undertake this quest do not survive, most often killed during the ordeals. As a result, those who do survive are hailed as the strongest demons to exist and are granted the title of Pluto, with demon Gairon being the very first to undertake and survive Hell's Pilgrimage.