stygian

['stɪdʒɪən]

1. hellish;: "Hence loathed Melancholy.../In Stygian cave forlorn"- Milton

2. dark and dismal as of the rivers Acheron and Styx in Hades;: "in the depths of an Acheronian forest"; "upon those roseate lips a Stygian hue"-Wordsworth