This precursor to the well-known HBO television series “Game of Thrones” ushers in the rule of House Targaryen. Almost 200 years before the events of “Game of Thrones,” “House of the Dragon,” which is based on George R.R. Martin’s “Fire & Blood,” tells the tale of the Targaryen civil war, in which King Viserys I Targaryen’s children fought for control of the Iron Throne.