Themes: Demonic, infernal entities, skulls, horns, screaming mouths, otherworldly monsters.

Aesthetics: Grisaille / monochrome (pencil, charcoal, ink), high detail, hyper-realistic texture.

Details: A lot of spikes, ragged edges, flowing "slime", smoke, fog, occult symbols (inverted crosses, pentagrams), the texture of charred flesh and bones.

Mood: Aggressive, brutal, occult, mystical, body horror, dark fantasy.

Experiment as much as you can)