Cinematic 8k wallpaper of a colossal Cthulhu emerging from turbulent waves near an old lighthouse perched on a moss-covered rock. The scene captures the chaos of a stormy sea with immense detail, as lightning illuminates the beast's intricate textures and monstrous presence. Light exudes an eerie, organic glow from within Cthulhu's form, providing a stark contrast against the dark, menacing sky. This hyperrealistic 4k digital painting showcases a centered composition, designed with meticulous attention to photorealism, featuring atmospheric lighting and lumen reflections. Each element is refined with subsurface scattering and exceptional detail, crafted to induce a sense of megalophobia. Utilizing advanced visual technologies like Unreal Engine 5 and Octane Render, the image is rendered with unparalleled sharp focus and cinematic quality, escorting viewers into a high-definition, immersive nightmare world.