Acheronian
Acherontic
Cimmerian
Lethean
Plutonian
Plutonic
Tartarean
chthonian
chthonic
clouded
cloudy
dark and gloomy
devilish
funereal
gloomful
glooming
gloomy
hellborn
hellish
ill-lighted
ill-lit
infernal
lowering
overcast
pandemoniac
pandemonic
purgatorial
somber
sombrous
stormy
sulfurous