According to a recent post, casting agents are looking for two female roles, "Rhaenyra Targaryen who they’re looking for someone in their late 20s for and Alicent Hightower who should be slightly older."
Following months of secrecy around the project, the casting rumor strengthens speculation that the series will focus on the two central figures in the Targaryen civil war otherwise referred to as the “Dance of the Dragons.”
The project is based on George R.R. Martin's Fire & Blood, a history of House Targaryen set 300 years before the events depicted in the hugely popular Game of Thrones series. HBO has reportedly committed to 10 episodes of House of the Dragon so far. According to the casting rumor, filming is currently scheduled to take place next year in the UK and Spain.