Cross Over! Acheron River
Shiryū, Shun, and Hyōga meet Dohko at the entrance to the pit where Seiya and Radamanthys fell. Saint of Libra tells them they must awaken their Eighth Sense in order to enter the world of the dead without getting killed. Source: crunchyroll
Aired 17/12/2005EP 1 - Cross Over! Acheron River
2005
Saint Seiya: The Hades Chapter - Inferno
Seiya and the rest of the Bronze and Gold Saints who have survived the Sanctuary battle have entered the world of the Dead. They are fighting to get to Hades and defeat him.
(Source: Anime News Network)