Cthulhu-like, tentacle monster, dark green slimy skin, glowing red eyes, sharp teeth, octopus-like legs, massive chest, powerful arms, ancient tome-bound hands, mysterious runes on the forehead, eerie bioluminescent markings, dimly lit, misty atmosphere, abandoned underwater ruins, coral reefs, seaweed-covered stones, ominous fog, horror ambiance, cinematic composition, wide-angle shot, shallow depth of field.