(adjective) shut off from the light; dark murky / (adjective) hard to understand; obscure / (adjective) causing gloom
"with the tenebrous incense of the oracular"
quoting Steiner
In some tenebrous manner, Hitler saw in the messanaic coherence of the Jewish people
they flatter the writer with the tenebrous incense of the oracular
there lurked a tenebrous techie will to power