Ballet as blood sport hardly begins to describe the audacious 'Black Swan,' director Darren Aronofsky's fever dream of paranoia, artistry and toe shoes. Don't be fooled by the rarefied milieu: 'Black Swan' is one of the best, lushest horror films since 'The Shining,' worthy of every inevitable comparison to the high-minded creep-outs of Cronenberg, Polanski and Lynch. As a prima ballerina coming unglued from forces either ghostly or psychotic, Natalie Portman justifies years of barely earned praise. She's as convincing in derangement as she is en pointe. Portman plays Nina, a New York City ballet dancer poised to become a superstar after being cast in a new version of 'Swan Lake.' Under the guidance of the company's Balanchine-like taskmaster (portrayed without a false note by Vincent Cassel), the technically proficient Nina is well-suited for the virginal White Swan, but she'll have to dig deep into something dark to bring out her inner Black Swan. Nina finds no respite from stress off stage. Her domineering, embittered mother (Barbara Hershey, her tight face perfect for the sickest mom since 'Carrie') barely tries to mask the cruelty beneath her attentiveness. A seemingly friendly understudy (Mila Kunis, in an actress-is-born performance) clearly has sinister motives. Whatever real-world knives are pointed at Nina's back are nothing compared to the spectral dangers lurking about. Portraits' eyes move, reflections have lives of their own, bloody scratches appear on Nina's shoulder and disgusting little black threads erupt from her skin. Someone or something is out to get her. Aronofsky ('The Wrestler'), with a screenplay by Mark Heyman, Andres Heinz and John McLaughlin, doesn't shy away from bump-in-the-night frights or creaky Freudian hokum. Bodily transformation, and the repulsion that goes with it, has been the stuff of horror films from Lon Chaney through 'The Exorcist.' Here, Aronofsky uses it to illuminate the physical self-destruction done in the quest for artistic perfection. He and cinematographer Matthew Libatique turn the elaborate preparation and donning of ballet slippers into an act of determined masochism, closer to Chinese foot-binding than costume. A small imperfection of the finger, no larger than a hangnail, is ripped from flesh like loose thread from a sweater. 'Black Swan' is as gross as it is frightening, and the art-house pretensions don't always keep up with the funhouse excesses. So what? Leaving the theater, I heard the phrase 'over the top' in two separate conversations. A fair assessment of any decent nightmare. _ _ _ 'Black Swan,' from Fox Searchlight Pictures, opens Friday in New York, Los Angeles, Boston, Washington, Chicago, Atlanta, Dallas, Houston and San Francisco. 