Important: from my preliminary tests, the slider adds darkness but you have to write where the darkness should be, background or foreground. See below for some keyword, but a good tag is 'chiaroscuro'.
I was tired of dramatic shadowing LoRAs that messed with my prompt, so I created my own LoRA that could mess with it!
Trained with figures in the shadows, or in backlight, dark background and dark foreground. Added concepts as negative, spot color, color contrast and something about double exposure. And, of course, chiaroscuro, from a selection of paintings.