What is the significance of using shadows and darkness on horror comics covers?

Shadows and darkness are fundamental to creating a sense of mystery, fear, and the unknown. They obscure details, allowing the viewer's imagination to fill in the gaps, often with something far more terrifying than what could be explicitly shown. They also create contrast, drawing attention to key elements and enhancing the overall dramatic effect. The use of chiaroscuro (strong contrasts between light and dark) is particularly effective.