HBO is set to develop another Game of Thrones spinoff. This time the network is going way back in time to Aegon's Conquest, according to The Hollywood Reporter.

Mattson Tomlin is in partnership with HBO to develop the project. He was an uncredited writer on Matt Reeve's The Batman and co-writer of its sequel The Batman Part II. Tomlin also co-wrote the feature adaptation of Keanu Reeve's comic BRZRKR, as well as the upcoming adaptation of the video game Mega Man.

House Targaryen 101: We begin with Aegon I

Aegon I Targaryen is Viserys I's (Paddy Considine in House of the Dragon) great-great grandfather, so this upcoming project is the closest direct prequel to the current HBO show. Just for reference: Aegon I's successor was Aenys I, his son with Queen Rhaenys. Aenys I's successor was his brother Maegor I, son of Aegon I's and Queen Visenya.

Maegor I's successor was his nephew, Jahaerys I, son of Aenys I and Queen Alyssa Velaryon. Which then gets us to his Jahaerys I's successor, his grandson Viserys I, son of Baelon and Alyssa Targaryen.

Aegon's Conquest, or just the Conquest, was Aegon I Targaryen's campaign to conquer most of Westeros. Along with his sister-wives, Visenya and Rhaenys, and their dragons Balerion, Vhagar and Meraxes, he subdued most of the Seven Kingdoms in two years, with exception of Dorne.

While it is called the Conquest, not all of the regions had to be taken by force. Some of the houses actively supported the Targaryens and the others willingly submitted.

A source described the series as a “back to basics” approach to George R.R. Martin's epic universe. It's a little unclear what this “back to basics” approach means when you consider the complexity of Game of Thrones was.

Since the end of Thrones in 2019, there have been many discussion on the prequels and sequels that would follow it. Some have been placed in development and some are no longer active. HBO refuses to name those that have been considered off the table because they may just be put back on with a different development team and writer.

There are currently two shows that have been greenlit: the second season of House of the Dragon which will premiere this summer and A Knight of the Seven Kingdoms: The Hedge Knight. The latter will begin production this year and is based on Martin's Dunk and Egg stories.

HBO has not officially commented on the news.