Dark Fantasy Fish-Headed Mermaid

Create a tall vertical dark-fantasy fine art illustration of a lone {argument name="mythic creature" default="fish-headed mermaid"} suspended upright in deep water, centered on the canvas. The creature has a pale corpse-white humanoid upper torso with gaunt anatomy, long thin arms, one hand pressed across the chest and the other hanging downward, stringy wet hair-like tendrils, and a large realistic fish head with one prominent round eye and a slightly open mouth. Its lower body is a long serpentine mermaid tail covered in countless overlapping metallic silver scales, tapering into a split fin near the bottom. The background is an abyssal navy-black textured wall or underwater void, with faint shafts of cold light descending from the top center. Add exactly two main vertical decorative areas: one narrow column of cracked white net-like geometric texture along the left edge, and one loose aura of irregular {argument name="metal accent color" default="gold"} leaf cracks and dripping lines surrounding the creature on both sides. Use an oil-painting mixed-media look with heavy impasto texture, scratched surfaces, tarnished metallic highlights, dramatic chiaroscuro, muted blue-black palette, eerie sacred-icon composition, and highly detailed scales and skin. No text, no border, no watermark.