tenebrous

I can't recall any other detail, but the whole atmosphere was tenebrous and sinister.

Winged things that were not bats swooped and fluttered in the tenebrous air, whispering sibilantly—whispering in human voices.

This spot, however small, is enough to betray his tenebrous nature.

Never had she looked to Ray so like an eagle, so keen, so fierce, so fit for braving either sun or tenebrous cavern.