Dictionary entry

Stygian

Webster's Dictionary 1913

Styg″i‐an (–an), a. [L. Stygius, fr. Styx, Stygis, Gr. Στύξ, Στυγόσ, the Styx.] Of or pertaining to the river Styx; hence, hellish; infernal. See Styx.

At that so sudden blaze, the Stygian throng

Bent their aspect. Milton.