Persephone, queen of the Underworld; wife of Hades and goddess of spring growth
Hecate was the goddess of magic, witchcraft, the night, moon, ghosts and necromancy.
Thanatos, god of death
Hypnos was the god or personified spirit (daimon) of sleep.
Hermes ,The guide of the dead who led the ghosts to their final resting place in Hades
Macaria, goddess of the blessed death
Melinoe, goddess (daemon) of propitiation’s to the ghosts of the dead
Angelos, Not much is known about her She was referred to as “She of the Underworld”
Eris was the goddess or personified spirit (daimona) of strife, discord, contention and rivalry.
Nemesis, the goddess (daemon) of indignation against, and retribution for, evil deeds and undeserved good fortune.
Nyx , goddess of the night
Erebus, the primeval god of darkness, his mists encircled the underworld and filled the hollows of the earth
Keres, goddesses of violent death, sisters of Thanatos
Styx, goddess of the river Styx
Acheron, god of the river Acheron
Alpheus, god of the river Alpheus
Cocytus, god of the river Cocytus
Eridanos, god of the river Eridanos
Lethe, goddess of the river Lethe
Phlegethon, god of the river Phlegethon
Palici – twin chthonic gods who presided over the geysers and underworld entrance
Erinyes, Chthonic deities of vengeance
Nymphs
Lampades, torch-bearing Underworld nymphs
Orphne, a Lampad nymph of Hades, mother of Askalaphos
Daeira An underworld Nymph and companion of the goddess Persephone. She was connected with the Eleusinian Mysteries.
Gorgyra An underworld Nymph. She was the wife of the River-God Acheron
Leuce (Leuke) A Nymph taken by thr god Hades to the Eleusinian fields where she was transformed into a white poplar.
Orphne An underworld nymph, the wife of the river Acheron.
Minthe An underworld nymph who had some sort of relationship with Hades (varies heavily) and ended up turned to mint most likely by Persephone.
Spirits
Keuthonymos, an Underworld spirit and father of Menoetes
Lamia, a vampiric Underworld spirit or spirits in the train of Hecate
Menoetes, an Underworld spirit who herded the cattle of Hades
Mormolyceia , a Underworld spirit or spirits in the train of Hecate
The Oneiroi were the dark-winged spirits of dreams
Cacodaemones (Kakodaimones) Evil spirits which issued forth from the underworld to cause harm.
Judges
Rhadamanthus, judge of the dead
Minos, judge of the dead
Aeacus, judge of the dead
Moirai
Clotho, “spinner” spun the thread of life from her Distaff onto her Spindle.
Lachesis, “allotter” or drawer of lots, measured the thread of life allotted to each person with her measuring rod
Atropos, inexorable" or “inevitable”, literally “unturning”, was the cutter of the thread of life. She chose the manner of each person’s death; and when their time was come, she cut their life-thread with “her abhorred shears”
Daemon
This only includes Daemons who are primarily underworld based so this list does not include beings like Nike, Eros, and other personified spirits of the human condition (which is what greek daemons tended to be)
Amphiaraus The prophetic Daemon of a subterranean oracle at Oropus in Boeotia.
Arae (Arai) The underworld Daemones of curses
Ascalaphus (Askalaphos) An underworld Daemon who tended the orchards of Hades
Ceuthonymus (Keuthonymos) A mysterious underworld Daemon. He was the father of Hades cattleman Menoetes.
Charon (Kharon) An underworld Daemon who ferried the souls of the dead across the streams of Acheron into Hades.
Eris was the goddess or personified spirit (daimona) of strife, discord, contention and rivalry.
Empusa (Empousa) A monstrous underworld Daemon with flaming hair, the leg of a goat and a leg of bronze.
Epiales The underworld Daemon of nightmares.
Eurynomus (Eurynomos) An underworld Daemon who stripped the flesh from the corpses of the dead. He was described with blue-black skin and was possibly imagined with a vulture’s head.
Melinoe A frightful underworld Daemon who led ghosts forth from the underworld to haunt the earth. One side of her body was coloured pitch black, the other was stark white.
Menoetes (Menoites) An underworld Daemon who herded the black-skinned cattle of Hades. He was wrestled by Heracles who cracked his ribs.
Nemesis, the goddess (daemon) of indignation against, and retribution for, evil deeds and undeserved good fortune.
Trophonius (Trophonios) The Daemon of the subterranean oracle of Lebadea in Boeotia.
Creatures
Cerberus the gigantic, three-headed hound of Hades which guarded the gates of the underworld and prevented the escape of the shades of the dead.
The Witch of the Web 