The HBO adaptation of George R.R. Martin's Game of Thrones has run out of George R.R. Martin books to adapt. Season 5, due to premiere April 12, will tie up Martin's A Dance With Dragons, the last book available in the series. And without another book coming in the near future , the series creators have to go ahead and make Season 6 without the roadmap they've used for so long.

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Alfie Allen (Theon Greyjoy)

Liam Cunningham (Davos Seaworth) and Carice van Houten (Melisandre)

Nathalie Emmanuel (Missandei)

Of course, Game of Thrones showrunnerDavid Benioff and screenwriter D. B. Weiss know how Martin's story ends, and have begun to write to his blueprints. But for the first time, the immediate future is completely unknown. To the Game of Thrones cast, this could either be a terrifying prospect or a liberating one - here's what Alfie Allen (Theon Greyjoy), Sophie Turner (Sansa Stark), Liam Cunningham (Davos Seaworth), Carice van Houten (Melisandre) and Nathalie Emmanuel (Missandei) had to say on the matter.Allen's Theon has had a rough time of it recently; most of us now know him as Reek, Ramsay Snow's mutilated plaything. But Theon's chronology has followed a markedly different path in the TV series than it did in the books."For me – specifically my character – with the torture stuff that happened in the third series", explains Allen. "In the books, it’s only really spoken of about twice [in the early books] – “Theon’s in the dungeons getting tortured” – that’s it. And so then that torture take place in book five. So they had to move it forward to season 3. So my storyline really is one where nobody knows where it’s going to go.""I'm feeling excited and terrified. It's a bit of both. Definitely. I try to get it out of David and Dan where it’s going to head, but they’re extremely tight-lipped... it’s more exciting than terrifying…but definitely a bit of both."van Houten and Cunningham, interviewed together as the devil and angel on Stannis' shoulder, are thrilled at the prospect of being unshackled - because neither have read the books. "I will get around to them," laughs Cunningham. "But everything's [always] been new to us.""It’s nice to know that now everyone is on the same page", says van Houten. "Nobody knows anymore. Like before in the make-up trailer, people would know a little bit more than we did... there were people who knew where it was going. Now everyone is on the same page."Cunningham stresses that the Martin/Benioff/Weiss trio are the only gatekeepers of Game of Thrones, and that's how it's going to remain."There’s only three people who knows how it ends. The middle of last year, the two boys, Dan and David, they spent a week with George in his home in Santa Fe, who rolled out the end of the story for them. So they know what’s going to happen."Emmanuel is excited to be moving away from preconceived notions of how the narrative should play out."Everyone has their opinions on the show because of the books", she says, "and now we’re walking into a season where nobody knows what’s going to happen. I think it’s exciting. I’m really excited to find out what’s going to come of Missandei and Daenerys."She could be on the winning team, I tell her."Well, we do have three dragons and a pretty kickass leader…so we’re doing ok. We're going to be ok."

Sophie Turner (Sansa Stark)

Sophie Turner explains that even with Season 5 under her belt, she still has no idea what's going to happen to Sansa in Season 6, calling her fate "the most ambiguous thing ever"."Um..it’s really exciting…I think", says Turner. "Especially because, for Sansa, as book fans will know, it’s kind of come to an end for her [storyline] in the books, so we don’t know what’s going to be in the next book for Sansa, but this season’s (Season 6) going to happen before then. So none of us have any idea. And judging by the end of how season 5 ends, I think it’s going to be the most ambigious thing ever what happens to her".

Game of Thrones Season 4 is out now in Australia, USA and UK on DVD and Blu-ray. Season 5 will premiere April 12.

Lucy O'Brien is Entertainment Editor at IGN AU. Follow her ramblings on Twitter.