Quentin Tarantino unchains America's tormented past in Django LOS ANGELES (Reuters) - Twenty years after Quentin Tarantino unveiled his first film "Reservoir Dogs," the director has turned his eye to America's slavery history, spinning a blood-filled retribution tale in his trademark style for "Django Unchained." Tarantino, 49, has become synonymous with violence and dark humor, taking on the Nazis in "Inglourious Basterds" and mobsters in "Pulp Fiction." In "Django Unchained," to be released in U.S. theaters on Christmas Day, he fuses a spaghetti Western cowboy action adventure with a racially charged revenge tale set in the 19th century, before the abolition of slavery in the United States. Jamie Foxx stars as a slave whose freedom is bought by a former dentist, played by Christoph Waltz. The two set off as bounty hunters, rounding up robbers and cattle rustlers before turning their attention to brutal plantation owners in America's Deep South. Tarantino is well-versed in delivering violence. But the director said he faced "a lot of trepidation" about filming the slavery scenes. He has already come under fire from some critics for the frequent use in the film of the "N-word" - a racial slur directed at blacks. The director said he was initially hesitant to ask black actors to play slaves who are shackled and whipped, and even considered filming outside of the United States. But a dinner with veteran Oscar-winning actor Sidney Poitier, whom Tarantino called a "father figure," changed his mind after Poitier urged him to not "be afraid" of his film. This movie is a deep, deep, deep American story, and it needed to be made by an American, and it needed to star Americans. ... Lots of the movies dealing with this issue have usually had Brits playing Southerners and it creates this arm's-distance quality," Tarantino said. Much of the film's more graphic slavery scenes, such as gladiator-style fights to the death and being encased naked in a metal hot box in the heat of the Southern sun, are drawn from real accounts. We were shooting on hallowed ground. This was the ground of our ancestors. ... Their blood was in the grass, there's still bits of flesh embedded in the bark," Tarantino said. The film has received good reviews from critics and is expected to add Oscar nominations in January to its five Golden Globe nods. With the exception of Waltz, who plays eccentric German bounty hunter Dr. King Schultz, the majority of the main players are not only American but from the South. It seemed sacred to us, and we couldn't help but channel those emotions, everybody on the crew and on the set. ... Those were very moving days," Tarantino said. Tarantino reunited with Waltz, who won an Oscar in 2010 for his role as a menacing Nazi officer in "Inglourious Basterds," and long-time collaborator Samuel L. Jackson, who plays slave housekeeper Stephen, a character who Tarantino described as "the most despicable black (character) " in movie history. "Stephen might be frankly the most fascinating character in the whole piece, and it was important to deal with that whole upstairs-downstairs aspect of the Antebellum South," he said. The role that has people talking is Leonardo DiCaprio's first villainous turn as a racist plantation owner - a stark contrast from his Hollywood heartthrob "Titanic" days and roles as eccentric Americans in "The Aviator" and "J. Edgar." Asked how he felt to be the first director to make DiCaprio a villain, Tarantino laughed, saying he felt "pretty darn good about it." He commended DiCaprio for turning into a "Southern-fried Caligula," referring to the tyrannical ancient Roman emperor. I saw him as a petulant boy emperor. ... He has nothing but hedonistic hobbies and vices to indulge him, and it's almost as if he's rotting from the inside," Tarantino said. The film's female lead, Django's wife Broomhilda played by Kerry Washington, moves away from Tarantino's fierce screen women such as Uma Thurman in "Kill Bill" and Diane Kruger in "Inglourious Basterds." Tarantino said Broomhilda was meant to be the "princess in exile." He said he was "annoyed" when he was asked by a friend why Broomhilda did not exact revenge on her abusers in the same way as Thurman's "Kill Bill" character. The film, he said, is "Django's story." "It invokes ... that odyssey that Django goes on and gives the black slave narrative the romantic dimensions of great opera or great folklore tales," Tarantino said. Editing by Jill Serjeant, Patricia Reaney and Will Dunham