Halfway into the first episode of Game of Thrones, an ambitious prince forces his gorgeous sister to marry a barbarian so he can gain the backing of the warrior’s army. Prince Viserys (played by Harry Lloyd) tells Princess Daenerys (Emily Clarke), “I would let the whole tribe fuck you — all 40,000 men and their horses, too — if that’s what it took.”

There are plenty of swords, horses, warring kingdoms and men in capes in HBO’s medieval fantasy, but Game of Thrones carves out its own territory by pushing all those Lord of the Rings-style conventions to the R-rated extreme.

The result is a show laced with violence, vulgarity and no shortage of nudity. In a conference call last week, series executive producers David Benioff and D.B. Weiss said they had no interest in diluting the adult-oriented source material created by George R.R. Martin in his multibook A Song of Ice and Fire saga.

“We wanted to keep the sexuality of the books,” said Benioff of the new show, which dramatizes the fantasy series’ first novel in a 10-episode run that starts Sunday. “We wanted to keep the profanity. We wanted the brothel scenes. We wanted the bloody violence. If someone’s head gets chopped off, you are going to see blood spurting out.”

Fans who adore the best-selling books can take comfort in the fact that Martin was consulted throughout production. Unlike Watchmen author Alan Moore, who disdains Hollywood’s makeovers of his material, former TV writer Martin contributed casting ideas and penned the second episode of the HBO show. He even had plenty to say about dragon design.

“George was a huge asset,” said Benioff, who earlier scripted Brad Pitt’s 2004 swordplay epic, Troy. “George has very definitive ideas about what dragons should look like because we wanted the dragons that he sees on-screen to closely mirror the ones that he had in his head.”

Judging from the succinct review proffered by Martin’s wife, Benioff and Weiss hewed true to the book’s spirit. At an advance screening, Weiss recalls, “She turned to us after it was over and said, ‘Guys, you didn’t fuck it up.'”

‘George has very definitive ideas about what dragons should look like.’

The big challenge in adapting Martin’s work for the screen relates to the sheer magnitude of storylines and characters. Early episodes center on the noble Stark family. Housed in the Winterfell castle, they rule a northern kingdom on the fictional continent of Westeros, but that’s just the tip of the infighting iceberg. Six other dysfunctional clans vie for power, which adds up to a lot of names and faces to keep straight.

In fact, much of the Game of Thrones pilot had to be reshot in order to clarify relationships between the sprawling cast of characters, Benioff said. “We’d showed the original pilot to very intelligent friends who watched carefully and, at the end, they had no idea that Cersei Lannister and Jaime Lannister were brother and sister.”

Game of Thrones‘ producers hope the thorny relationships and bloody encounters draw a big enough crowd to justify six more seasons encompassing all of Martin’s Song of Ice and Fire material.

“George is brutal,” Benioff said. “He’s rough on his characters. Anyone and everyone is at risk of getting his or her head lopped off. That makes the show very tense and will hopefully keep people tuning in every week.”

Game of Thrones premieres Sunday at 9 p.m. on HBO.