A new blog post by George R.R. Martin following the series finale of Game of Thrones teases that the author has been helping make a video game.

The blog post says that he’s been busy lately, and even “consulted on a video game out of Japan.” While those details aren’t too specific, a source told Gematsu that From Software is working on an unannounced title with Martin, known internally as “GR.” The Gematsu report also notes that the title will be officially announced at Microsoft’s E3 press conference this year and it’s a collaboration between Martin and Hidetaka Miyazaki (known for his Souls series).

The source explains that the game has been in development for three years already, and is an open-world game with horse riding. It will be published by Bandai Namco.

Original speculation about Martin creating a Souls-like game with From Software spawned from a tweet from Liam Robertson: “There is a From Software rumour going around that is absolutely bonkers. I think you should be hearing some more about this later today.” The rumors only continued following Spawn Wave’s video talking about a collaboration with the Game of Thrones writer.

The Microsoft E3 press conference takes place on June 9, so we’ll have to wait until then for more information.

Update: A previous version of this story said that the game would include “horse racing” instead of “horse riding.” This has been fixed above.