Hades refers to the Greek god of the underworld and his dominion where souls reside. Ancient Greeks would offer sacrifices to appease the god Hades.
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Not Always Evil
In Greek stories, Hades is not inherently evil; it's simply the afterlife's place of the dead. Hades was feared but not loathed as he ruled over the dead.
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Used Literarily
Hades is used for dramatic effect in literature, often referencing the afterlife or death. The hero's journey took him to the depths of Hades.