(adjective) shut off from the light; dark murky / (adjective) hard to understand; obscure / (adjective) causing gloom
The poet's dream stole over him like sunlight
And passed into the tenebrous thickets.
"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