There is a fifth potential Game of Thrones prequel series in the works, and this one hails from GoT co-executive producer Bryan Cogman, Deadline has confirmed. The project is currently in early development. HBO noted earlier that there is no set timetable for the possible series, and all will be evaluated when scripts are completed.

The fifth possible prequel was mentioned cryptically by George R.R. Martin in a blog post a few months ago.

HBO confirmed back in the spring it had signed deals with four writers to join Martin in the development and writing of four offshoot series. They are Max Borenstein (Godzilla, Kong: Skull Island), Jane Goldman (Kick-Ass, Kingsman and X-Men franchises), Brian Helgeland (Mystic River, A Knights Tale) and Carly Wray (HBO’s The Leftovers & Westworld, AMC’s Mad Men). Cogman is now the fifth.

The nearly 80-minute long “The Dragon and The Wolf” Season 7 finale penned by David Benioff and D.B. Weiss snagged 12.1 million viewers, up 36% over the Season 6 finale. Set to be a six-episode run, the eighth and final season of the Emmy-winning series is expected to debut next year.

Cogman is repped by UTA and Management 360.

EW first reported a fifth prequel series was in the works.