The Darkness pantheon is an unusual in that most of these cults are worshiped primarily or even exclusively by non-humans. Darkness is deadly, fearsome, devouring, crushing, cold, silent, secretive, and mysterious, and many of these deities manifest these powers. It is not unreasonable for mortals to fear the dark!
Darkness was born in the Underworld, or perhaps is better thought of as the Underworld. “From Darkness we emerge and to Darkness we go,” is a common saying in many religions. Shades, demons, and ghosts inhabit the Darkness, as well as insects, spiders, fungus, and trolls.
Trolls are the main worshipers of these deities, and they have deeply embraced the mythology of Darkness to the near-exclusion of others.