stygian – dark, gloomy, infernal or hellish
We are probably all familiar with the term ‘stygian gloom’ to describe a certain type of darkness. Thick and all consuming, only traces and outlines are visible within. Stygian is of or relating to the river Styx (In Greek mythology, Styx is a deity and a river that forms the boundary between Earth and the Underworld or Hades).
C16: from Latin Stygius, from Greek Stugios, from Stux Styx ; related to stugein to hate.