tenebrosity
noun
ten·e·bros·i·ty
-sətē,
-i
plural -es
: darkness
switches off the light, calls for the first slide, and talks for three quarters of an hour in Stygian tenebrosity 
Lancet
Lancet
Word History
Etymology
Medieval Latin tenebrositat-, tenebrositas, from Latin tenebrosus dark + -itat-, -itas ity