The Underworld (Ἀΐδαο δόμος) — mythic land of Homer's Odyssey

The Underworld — Where the dead drink blood and speak. The Nekyia: the Summoning of the Dead (Od. 11).

At the fog-bound rim of the world, beyond the stream of Ocean, stands the House of Hades. Odysseus came here alive, dug a pit, and bled two black sheep into it — and ten years of ghosts came up to drink. He left with a prophecy, a broken heart, and the bitterest line in Greek poetry.

Circe's sailing directions were simple and terrible: cross the stream of Ocean to the fog-bound land of the Cimmerians, where the sun never breaks through. The outer approaches are ashen fields under permanent cloud — a grey country of black poplars and fruit-dropping willows, Persephone's blighted grove. Only at its heart does the ground open: the pit itself, where Acheron, Pyriphlegethon and Cocytus crash together at a great rock. The crew beached the ship and walked in silence. Nobody makes small talk on the road to the door of Hades.

At the meeting of the rivers Odysseus dug a trench a cubit square and poured the dead their drink: milk and honey, sweet wine, water, white barley. Then he cut the throats of a black ram and ewe, and the blood ran dark into the pit — and they came. Brides, unwed youths, old men who had suffered much, warriors still in their bloodied armour, drifting up out of Erebus with an unearthly cry. He crouched over the trench with drawn sword, holding back the massed dead from the one thing that could make them speak.

The first face was the worst: Elpenor, his own crewman, unburied and unwept — he had fallen off Circe's roof that very morning, and his ghost had outpaced the ship. Then Teiresias of Thebes drank and spoke the future plainly: Poseidon's grudge, the fatal cattle of the Sun on Thrinacia, the suitors gorging in his hall at home, and at the very end a gentle death coming 'from the sea.' Then his own mother, Anticleia, dead of grief for him. Three times he reached to embrace her; three times she sifted through his arms like shadow.

After her came the parade: queens and heroines sent up by Persephone, then the comrades of Troy. Agamemnon, murdered at his own homecoming feast, warning him to trust no wife entirely. Achilles, who cut through every consolation with the bitterest line in Greek poetry — better a hired hand alive, serving a landless nobody, than king over all the perished dead. And Ajax, who would not speak at all, still furious over the armour of Achilles, turning away into Erebus with his silence intact. Some grudges outlast the grave.

Deeper in, the torments: Tantalus straining after receding water, Sisyphus shouldering his boulder up the endless slope, the phantom of Heracles with an arrow forever notched. Then the dead began to mass in their tens of thousands with a shriek, and a cold thought seized Odysseus: what if Persephone sent up the Gorgon's head? He ran for the ship. Even the man who out-talked the Cyclops knows when a conversation is over.

Denizens

Hades (ᾍδης) — Lord of the house that bears his name; never appears on stage, which somehow makes it worse.
Persephone (Περσεφόνεια) — The dread queen who marshals the shades — and who could, at any moment, send up the Gorgon's head.
Teiresias (Τειρεσίας) — The blind Theban seer, the one shade who keeps his wits even in death; he drinks the blood anyway, for form's sake, then tells Odysseus everything.
Anticleia (Ἀντίκλεια) — Odysseus' mother, dead of longing for her missing son; thrice embraced, thrice smoke.
Elpenor (Ἐλπήνωρ) — Youngest of the crew, neither brave nor bright by Homer's own account; first ghost at the pit, politely requesting a funeral.

Perils

Thirsty ghosts: Every shade in Erebus wants a sip of that blood, and there is exactly one pit. Bring a sword and a firm no.
Emotional ambush: You will meet your dead mother here without warning. Homer confirms she cannot be hugged; three attempts is the canonical number.
The Gorgon clause: Linger too long and Persephone may send up the Gorgon's head. Nobody has stayed to verify. That is rather the point.
One-way geography: The pit is easy to find and the exit is a rumor. Park the ship where you can run to it.

The crew's toll: 0 lost below — 1 lost just above — Hades claimed nobody, but Elpenor fell off Circe's roof at dawn and beat the ship to the Underworld. His ghost's one request: bury me properly, and plant my oar on the mound.

“I would rather live on the soil as another man's hireling than be lord over all the perished dead.” — Od. 11.489–491 (Achilles)

Traditional location: Lake Avernus and the Phlegraean Fields, Campania, Italy. A birdless volcanic crater lake near Cumae, ringed by sulphur fields, where the classical world fixed the mortal doorway to Hades — the map's outer wash marks the ashen approaches, the inner ring the pit itself at Avernus.