Abzu

Abzu (the god of darkness) was God who created all univeso the darkness, and his seven elements (water, fire, earth, wind, thunder, light and shadow), therefore, a major god. However, the Earth was dominated by the Olympian gods, including Zeus, who gave the planet for his daughter, Athena; thus the Earth probably did not use its 7 elements. But Medea invoked a meteor that brought the soul of Abzu to Earth, along with two babies representing each of the two dominant elements: Light and Shadow; the presence of Abzu on the planet, made the cosmos there to use his seven elements. Babies were Aria, representing the light, and was created by Mars (to do things your cosmos of darkness was not), and Kouga, who was supposed to be possessed by the god of darkness at the time, but the light cosmos of Athena saved him. Abzu was sleeping in Kouga, which now has a light cosmo borrowed by Athena.

After Medea enter Kouga darkness, the light of Athena went off inside him, and so Abzu awake. After much effort, Seiya and Yuna expel Abzu of Kouga, and Kouga comes into its darkness and defeat his original body.