House of the Dragon proved to be a major success (even bigger than anticipated) for HBO, so it was probably only a matter of time before more Game of Thrones spin-off shows were announced. Now, Variety is reporting that another prequel series that would take us back even further than the events of the Dance of the Dragons is in the very early stages of development.
According to the trade, this show would focus on Aegon I Targaryen’s conquest of Westeros.
Nothing has been grenlit yet, so no writer is currently attached, though sources say that the "search is underway as HBO is keen to move forward and get it into development."
Apparently, a feature film that would lead directly into the series is also being discussed, but details are few and far between.
If the show does move forward, it will tell the story of how "Aegon and his sister-wives, Visenya and Rhaenys, used their army and their three dragons to conquer six of the seven kingdoms on Westeros with the exception of Dorne. In doing so, Aegon I became the first king of Westeros, the first to sit on the Iron Throne, and the founder of the Targaryen Dynasty. Those events took place approximately 300 years prior to the events of Game of Thrones."