Stygian describes darkness that is total, and that feels frightening rather than merely dark. The commonest phrase by far is 'Stygian gloom' or 'Stygian darkness' — the kind of blackness in a cave, a tunnel, a cellar, or a moonless night in the countryside, where you cannot see your own hand and something in you wants to turn back. It carries the flavour of the underworld, of death, of a place the living should not be. The word comes from the river Styx, the river of the dead in Greek myth, so its literal meaning is 'belonging to the Styx'. Because of that, writers sometimes stretch it beyond darkness to mean 'hellish' or 'of the underworld' generally: Stygian depths, a Stygian atmosphere in a grim place. This is a literary word. You will find it in novels, ghost stories, travel writing, and dramatic journalism; nobody says it at dinner. Because it is a proper name underneath, it is usually written with a capital S, though you will see lowercase 'stygian' too, especially in the loosened 'very dark' sense. It is pronounced STIJ-ee-un, with a soft 'j'.

如冥河般漆黑的、幽暗陰森的（源自希臘神話冥河 Styx，屬文學用語）