Stygian manes have a vaguely reptilian or fish-like appearance, with a slick rubbery hide and yellowish spines that begin at their brow and protrude all the way down their back. The fangs of a stygian mane drip with horrid venom.

Stygian manes are most often found in the Stygian Swamps of the Abyss, where demon lords recruit them as guards and chattel minions. Although seldom encountered outside of Styx, the Abyss, and the Rings of Hell, they can be encountered in the mortal realms as summoned minions or in thin spots between the planes.