Excellent news, Game of Thrones fans: HBO is expected to greenlight another spin-off very soon.

Sources tell Deadline that the cable network is nearing a pilot order for a series centered on House Targaryen. According to the outlet, the untitled prequel will be set 300 years before the events of GoT, around the time the Targaryens began to fall. The series will be based on George R.R. Martin's Fire & Blood book, which lays out the history of the family. Ryan Condal—the co-creator and co-executive producer of Colony—has reportedly signed on to write the pilot script.

Martin teased the GoT "successor shows" on his blog earlier this year, telling readers that three of the five potential series were "moving forward nicely." 

"The one I am not supposed to call THE LONG NIGHT will be shooting later this year, and two other shows remain in the script stage, but are edging closer," he wrote. "What are they about? I cannot say. But maybe some of you should pick up a copy of FIRE & BLOOD and come up with your own theories."

The pilot for the GoT spinoff starring Naomi Watts was shot earlier this summer and is now awaiting the official green light.

According to HBO, the Jane Goldman series will chronicle "the world’s descent from the Golden Age of Heroes into its darkest hour. And only one thing is for sure: from the horrifying secrets of Westeros’ history to the true origin of the white walkers, the mysteries of the East to the Starks of legend … it’s not the story we think we know."

Stay tuned as more details about the prequels become available. 

The GoT series finale aired back in May, more than eight years after its premiere.