According to Miyazaki, Martin did not write the main story of Elden Ring. Rather, he wrote the events that happened long before the era the player explores—in other words, the “mythology” of the world. Miyazaki said that there were two reasons he had Martin write the mythology rather than the main story.
“Storytelling in video games—at least the way we do it at From Software—comes with a lot of restrictions for the writer. I didn’t think it was a good idea to have Martin write within those restrictions. By having him write about a time the player isn’t directly involved in, he is free to unleash his creativity in the way he likes. Furthermore, as From Software we didn’t want to create a more linear and story-driven experience for Elden Ring. Both issues could be solved by having Martin write about the world’s history instead.”
According to Miyazaki, the excitement, drama, and depth in the mythology written by Martin had a major impact on From Software’s creation of the world for Elden Ring.
Miyazaki compared Martin’s mythology to the dungeon master’s handbook in a tabletop RPG.