HBO's Game of Thrones has already started to depart from the book series it's based on, and seeing as it plans to wrap up before George R.R. Martin's novels have finished, that seems almost necessary. Now it looks like the show might be departing even more, killing off people who didn't die in the books.

According to Showbiz 411, author of the Song of Ice and Fire series George R.R. Martin said people will die this season who don't die in the books and that will probably make book readers unhappy, joking that showrunners David Benioff and D.B. Weiss are even bloodier than he is. "So everybody better be on their toes."

So who exactly could Martin be referring to? Well, Game of Thrones has actually already done this before, but mostly to characters who aren't that significant to the story. The show killed Daenerys' handmaiden Irri although she's still alive in the books, but Irri was never a significant character, so this didn't really have any big implications. Grenn and Pyp also died in the Battle of the Wall last season though they survived it in the books, but their roles in the story could easily be shifted to someone else.

Is it more of this kind of thing that Martin is referring to then? Or could it be someone more significant? Readers are already beginning to speculate about which character could be killed off. Martin is probably referring to supporting characters, but there are a few from the books who as of A Dance with Dragons have had a minor enough role that they could easily be killed off.

Here's what interesting about this, though: how Game of Thrones handles killing off these characters might actually be spoiling what's going to happen in George R.R. Martin's book series. Showrunners Benioff and Weiss have been told the ending of the Song of Ice and Fire series so that they could start to work towards it in the show, according to Slashfilm. So if a character is killed off on the show who is still alive in the books, that might pretty much confirm that they won't do anything too significant in future books. If someone dies in the show, he or she probably isn't making it to the Iron Throne in the books.

As an example of this phenomenon, one recent change from the book series was that in the TV show, Robb's wife dies at the Red Wedding, where as in the book series she is still alive. This has lead many to believe that her character and her baby will not be that important in the next few books because if so George R.R. Martin would have told the showrunners to keep her alive.

There was once a time when reading the Game of Thrones book series spoiled what was going to happen in the show, but now watching the Game of Thrones TV show might end up spoiling what's going to happen in the books.

Of course, this might not always be the case. The showrunners know the broad strokes of the ending, like who will end up on the Iron Throne, but it's not totally clear how much of the nitty-gritty details they've been told. It's also true that some storylines will have to be cut from the series not because they are't important to the books, but just because there isn't enough time for them. With a series that probably only has a few seasons left, the showrunners need to start trimming at some point.

Speaking of length, it has been said before that Game of Thrones would probably run for seven seasons, but could it be more than that? Martin told Showbiz 411 that they could have a 7th, an 8th or even a 9th; nobody really knows. So it really isn't clear how long the series could run for, but the fact that Martin is open to more seasons shows that HBO isn't totally firm in their seven season plan, just as Martin doesn't seem to be 100% firm in his seven book plan.

Game of Thrones returns for its fifth season on April 12.

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