HBO is reportedly eyeing another, yes another, Game of Thrones prequel series

gamesradar.com:

HBO is reportedly "actively considering" yet another Game of Thrones prequel series, this time about Aegon's Conquest.

According to Variety (opens in new tab), very early discussions are being had about a Game of Thrones prequel that would explore events taking place more than 100 years before House of the Dragon, itself a prequel taking place almost 200 years before Game of Thrones. Aegon's Conquest is the name referring to the campaign led by Aegon I Targaryen to conquer most of the Seven Kingdoms alongside his sisters, Visenya and Rhaenys, and their dragons, Balerion, Vhagar, and Meraxes. This event kicks off the novel Fire & Blood and kickstarts the branching off and fracturing of the Targaryen family that would eventually culminate in the events of House of the Dragon. 

Fun fact: Game of Thrones and House of the Dragon take place in a world that documents its own history with "AC" and "BD," referring to "After Conquest" and "Before Conquest." That alone should tell you how impactful the events of Aegon's Conquest are to the entire world of Westeros and the story of A Song of Ice and Fire, the series of novels the HBO series are based on.

It's important to note that while Variety reports that early discussions are being had around another Game of Thrones prequel, there still isn't a writer attached and it's as yet uncertain whether the series will ever get the green light from HBO. In fact, in a statement to IGN (opens in new tab), HBO called Variety's reporting "speculation without our participation."

There are numerous other Game of Thrones prequels in various stages of development at HBO, including one based on A Song of Ice and Fire author George R.R. Martin's novella, Tales of Dunk and Egg, and another based on