In my novel, there's something that the characters refer to as "darkness". It symbolizes the bad thoughts of depressed/suicidal people.
A short silence. I imagined Joel nodding his head in the dark. "After an outing, you feel as if something has crept inside you. Something dark and murky, like crude oil. It travels gradually, silently, polluting every cell in your body. You can feel it. Eating you alive. And the worst part is, you're the only one who's aware of it. Yes, you can explain it to people, but just skin-deep. They can't help you. So you have no choice but to fight alone. Fight this darkness alone."
Perhaps this darkness, despite coming from the same source, varied depending on the person. Like when you press a drop of ink between two sheets of paper. Sometimes you get a butterfly. Sometimes a face. And other times a shape so amorphous it doesn't resemble anything at all.
Was this the darkness Joel had talked about?
How should I format this word? Italics? Capital? Should it be formatted differently when it is first mentioned?