stygio, stygi-, styx-

(Greek > Latin: hate, hating, hated, hateful; abhor, abhorrence; loathsome, loathing)

Literally, the “horrible”. Related to "chill, frost; hate, hatred; abhorrence"; originally, "to shudder with cold"; by extension, hell or hades.

Stygian, stygian
1. Of or characteristic of the river Styx and the infernal regions.
2. Pertaining to the river Styx, or, in a wider sense, to the infernal regions of classical mythology.
3. Infernal or hellish; dark or gloomy; inviolable.
4. Completely binding, as an oath sworn by the river Styx, which the gods themselves feared to break.
5. Very dark, as a Stygian crypt.
stygiophobia
An abnormal fear of hell; also, hadephobia.
Styx (s) (noun) (no plural)
Literally, the Hateful. In Greek mythology, the river encircling Hades over which Charon ferried the souls of the dead to the underworld.

According to Homer, the underworld is vague, a shadowy place inhabited by shades. The existence of ghosts, if it can be called that, was like a miserable dream. The later poets defined the world of the dead more and more clearly as the place where the wicked were punished and the good rewarded.

The Roman poet Virgil presented in great detail the torments of the one class and the joys of the other. Virgil is said to be the only poet who gave a clear geography of the underworld. The path down to it led to Acheron, the river of woe, which poured into Cocytus, the river of lamentation. An aged boatman named Charon ferried the souls of the dead across the water to the farther bank, where the adamantine gate to Tartarus stood.

Charon would receive into his boat only the souls of those upon whose lips the ferry-passage money (a small coin known as the obol) was placed when they died and who had received the rites of burial. All the others were driven back by the ferryman’s long oar. These were obliged to wait one hundred years before they might at last hope to enter Charon’s boat.

On guard before the entrance to Hades sat Cerberus, the three-headed, dragon-tailed dog, whose neck bristled with serpents and whose dreadful baying terrified all who approached.

Cerberus was put there by Pluto to make sure that no shade escaped to return to the upper world after he/she once entered the realms of the dead.

—Compiled from material located in the following sources:
Crowell's Handbook of Classical Mythology by Edward Tripp;
Thomas Y. Crowell Company; New York; 1970; pages 538-539.
and
Dictionary of Classical Mythology by J.E. Zimmerman;
Harper and Row Publishers; New York; 1964; pages 249-250.

Three other rivers, besides Acheron and Cocytus, separated the underworld from the world above:

Phlegethon, the river of fire; Styx, the river sacred even among the gods (and mankind), for by it they sealed their unbreakable stygian oaths which they dare not break; and Lethe, the river of forgetfulness.

Anything pertaining to the Styx, and therefore to the underworld is said to be “Stygian”. This word is particularly used in the phrase “stygian darkness” meaning a great darkness, the darkness of the underworld.

Once within Hades, the spirits of the dead drank from a river named Lethe (forgetfulness) so that having drunk, they forgot about their former life and became listless, gibbering ghosts.

We now speak of anything that causes forgetfulness as “Lethean”. One is liable to be forgetful if he/she is sleepy or sluggish, and we are then said to be “lethargic”. Since complete forgetfulness comes only with death, we speak of anything deadly as “lethal”.

The condemned were assigned to regions where all manner of torment awaited them at the hands of terrible monsters; such as, the fifty-headed Hydra and the avenging Furies.

Some evildoers; such as, the Titans of old, were doomed to languish in the gulf of Tartarus farther below; but the souls of the guiltless passed to the Elysian Fields, where each followed the chosen pursuit of his/her former life in a land of spring, sunlight, happiness, and song.

By the Fields there flowed the river Lethe, from which the souls of those that were to return to the earth in other bodies drank, resulting in the oblivion of their former lives.

Some people still speak of Elysium as a place or time of great happiness and even sometimes use it as another name for “heaven”. The French words for Elysian Fields are “Champs Elysées” [shahn zay lee ZAY] which is the name given to a “famous and fashionable” tree-lined boulevard leading from the Place de la Concorde to the Arc de Triomphe in Paris.

—Compiled from contents located in:
Mythology Greek and Roman by Thomas H. Carpenter and Robert J. Gula;
Longman Publisher; New York; 1977; pages 76-77.

Related "hate, hatred" word sources: miso-; odi-.