Painstaking Attention To Details, Craft a mesmerizing masterpiece depicting a dark fantasy octopus, its tentacles swirling and undulating with an otherworldly grace. The creature's massive, shadowy form looms ominously against a backdrop of eerie, bioluminescent waters, casting a haunting glow upon the surrounding marine life. Its eyes, deep and mysterious, gleam with an otherworldly intelligence as it navigates the murky depths with a sinister elegance. The octopus's skin is a tapestry of intricate patterns and textures, shimmering with an iridescent sheen that hints at its supernatural origins. Each tentacle is adorned with rows of razor-sharp suckers, poised to ensnare any unsuspecting prey that dares to venture too close. The scene exudes a sense of dark beauty and danger, inviting the viewer to delve into the enigmatic depths of this fantastical creature.