HBO is in talks to produce a Game of Thrones prequel, this time about the origins of the House Targaryen.

The prequel series is slated to take place three centuries before the start of Game of Thrones and closely follows “the beginning of the end” of the House Targaryen.

The series is set to follow George RR Martin’s book Fire & Blood, the first volume of the two-part history of the Targaryens in Westeros. HBO declined to confirm the prequel series, which has been in the works since last fall, and no official title has been released.

So far, one Game of Thrones prequel with the working title Bloodmoon, starring Naomi Watts and set thousands of years before the events of the show, has been announced.

As for when Martin will finish the books, the author maintains he is still working on it.