A geometric grand piano submerged in the deep sea, dark fantasy and sci-fi style. The piano body is constructed from dark obsidian with sharp, angular, futuristic geometric shapes. Partially encrusted with bioluminescent fractal corals and glowing neon abyss-blue veins. The keys are made of translucent crystal and tarnished brass. Intricate mechanical and alien geometric structures. Ethereal underwater atmosphere, highly detailed, 4k resolution, PBR textures, Octane Render, Unreal Engine 5, masterpiece, clean 3D topology.