Sty ‧ gi ‧ an /ˈstɪdʒiən/ BrE AmE adjective [usually before noun] literary
[ Date: 1500-1600 ; Language: Latin ; Origin: stygius , from Greek , from Styx river in ancient Greek stories which people cross over when they die ]
unpleasantly dark, and making you feel nervous or afraid:
the Stygian gloom