In a lot of the dark fantasy I gravitate towards, gothic demons aren't just random monsters waiting to be slain. They're more like walking, talking atmospheric conditions. They ARE the gloomy manor house, the oppressive forest, the sense of ancestral sin. Think of the demon in 'The Invisible Life of Addie LaRue'—it's less about hellfire and more about this chilling, elegant weight of history and a bargain that seeps into every corner of a life. Their power comes from ritual, from pacts, from words spoken in old languages, not just brute strength. That makes them scarier, in a way, because you can't just stab a metaphor.
They also serve as fantastic foils for exploring human morality. When a character is faced with a demon offering a deal, the real horror isn't the demon's appearance; it's seeing what the human is willing to give up, what they're willing to become. The demon just holds up a mirror. I find that far more compelling than a simple good-versus-evil battle. It turns the story inward. The gothic demon's role is to corrode, to tempt, to reveal the cracks in the protagonist's soul that were already there, hiding under the surface of their genteel or ordinary life.
Sometimes they even become romanticized, which is its own whole subgenre rabbit hole. But even there, the gothic roots mean the relationship is never sunshine and rainbows. It's always tinged with danger, decay, and that addictive pull toward the abyss. The demon is both the threat and the allure, which is a classic gothic duality. It’s why we keep reading—to see if the character will be consumed or somehow, against all odds, find a way to harness that darkness without losing themselves.