This monster is based on the Sun. The Legendary Planet series from the same storyline are based on the planets that orbit it.
Despite the Sun being very bright, and being the source of life, this monster is DARK-Attribute and Fiend-Type, a creature that represents destruction rather than life. In the storyline of the manga, Tragoedia designed the card this way to mock the sun-worshipping priests who had punished him. This card's Attribute reflects this card's background image making it dark.