Martin, who has written book series 'Song of Ice and Fire' which the hit fantasy drama is based on, said no character is safe in the story, reported Aceshowbiz.
"I have a large number of important characters who I switch between to tell the entirety of the story, and that limits who I can kill.
"Sometimes there's only one character who's my eye in a particular location, and if I kill that character, everything going on in that particular subplot is going to be lost," he said.
The viewpoint characters are meeting up with each other and being in the same point at the same time, which gives me a lot more flexibility for killing people," Martin added.
The sixth book 'The Winds of Winter' is still in progress. There is one more chapter left, 'A Dream of Spring', before the saga finally comes to a close. The show's fifth season will air next year.