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)

Hades is planning to take over the world, to achieve that goal, he sends out deceased Gold Saints to take Athena's head. Seiya and the other Bronze Saints come to help but their help isn't appreciated by the remaining Gold Saints that are still alive.
 
(Source: Anime News Network)

After the 12 Gold Saints sacrifice their lives to destroy the Wailing Wall, The Bronze Saints enter the deepest realm of the Underworld, Elysion, where they face off aganist Hades's two most powerful servants: The Twin Gods, Hypnos and Thanatos, before they can reach Hades for the final battle.

In Greek mythology, Athena, the daughter of Zeus, was born in full armor. By birthright the goddess of battle, she did not believe in conquest, and only fought defensive wars. Her battles with bloodthirsty gods and giants shook the very earth and seemed to last forever. On the battlefield, there were a group of youths that always surrounded and protected the goddess: the Knights of Athena! Flash forward to modern-day Greece: two Japanese tourists are shocked to see a mansized meteorite crash to the earth before them. It turns out to be young Seiya. Seiya must train harder than ever if he is to survive his match with the brutal Cassios! Whoever wins will receive the greatest prize known to man: the incredibly powerful Pegasus Cloth!
 
(Source: Viz Media)
 
Note: The chapter count includes 247 regular chapters and 2 extra chapters ("SHAKA" and “The Cygnus Story - Natassia of the Land of Ice”), other editions merge chapters into a total of 110 chapters.

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