dark vs Stygian

dark is a noun but Stygian is not a noun.

Word	Noun	Adjective	Verb	Adverb
dark	Yes	Yes	No	No
Stygian	No	Yes	No	No

dark (noun)	Stygian (noun)
an unenlightened state
an unilluminated area
absence of light or illumination
absence of moral or spiritual values
the time after sunset and before sunrise while it is dark outside

dark (adjective)	Stygian (adjective)
devoid of or deficient in light or brightness; shadowed or black	dark and dismal as of the rivers Acheron and Styx in Hades
(used of color) having a dark hue	hellish
brunet (used of hair or skin or eyes)
secret
causing dejection
stemming from evil characteristics or forces; wicked or dishonorable
showing a brooding ill humor
not giving performances; closed
marked by difficulty of style or expression
lacking enlightenment or knowledge or culture