Rumor has it that A Song of Ice and Fire author George R. R. Martin has worked on an upcoming, unannounced game with FromSoftware and Dark Souls creator Hidetaka Miyazaki, and now some Reddit users believe they’ve found clues about it hidden in the game files for Sekiro: Shadows Die Twice.

As GamesRadar+ reports, modder TKGP spotted a curious path in Sekiro’s material configuration files. The path points to a folder titled “GR,” which TKGP reckons is short for “Great Rune,” the codename for FromSoftware’s upcoming title.

Apparently there was a sneaky little reference to Great Rune sitting here in the Sekiro material configs all along. pic.twitter.com/H5uKZOUzZiMay 29, 2019

That’s different from the standard folder for Sekiro assets, which are stored in a folder called “NTC.” Modders aren’t sure what exactly that stands for, only that it’s the abbreviation FromSoft uses for Sekiro.

Reddit user Kalash believes this is a strong indication that Great Rune is currently in active development, and that it’s being built in FromSoft’s internally-developed game engine rather than in Unreal Engine 4, as some rumors had previously suggested. That's based on the reference to a map called "m99," which is debug level From uses for its engine.

Granted, an asset folder with a two-letter name isn’t a lot to go on, but it bears remembering that FromSoftware delights in hiding little hints and secrets around its games: there’s a character in Bloodborne who looks an awful lot like the Wolf from Sekiro, for example.

Hopefully we’ll learn more about Great Rune—or whatever it’s going to be called—at E3 in a couple weeks.