Actor Graham McTavish is trading the Scottish Highlands for the Westeros Crownlands.
House of the Dragon takes place hundreds of years before the events of Game of Thrones during the height of the Targaryen empire in Westeros. McTavish's Harrold served in the Kingsguard during the reign of King Jaehaerys I Targaryen, and he remained among the ranks when King Viserys I Targaryen (Paddy Considine) ascended the Iron Throne.
Described as a paragon of chivalry and honor, Harrold now essentially serves as the royal escort and bodyguard to Viserys' daughter, Princess Rhaenyra Targaryen. (Milly Alcock plays Rhaenyra as a teen and Emma D'Arcy plays the character as an adult.)
Ollie Upton/HBO 'Outlander' star Graham McTavish appears as Ser Harrold Westerling of the Kingsguard in HBO's 'House of the Dragon.'
The young Rhaenyra is named Viserys' chosen successor to rule Westeros when the time comes, but when the king conceives a male heir in the proceeding years, House Targaryen and their supporters are divided. This leads to the central conflict of House of the Dragon: the Dance of the Dragons, the name given to the bloodiest civil war in Westeros' history.
"I wanted to tell a story about the height of Rome before the fall and see the Targaryen dynasty at its very apex so that we can understand the thing that was lost when it all falls apart," executive producer Ryan Condal tells EW. (Condal co-created House of the Dragon with A Game of Thrones author George R.R. Martin and serves as co-showrunner alongside Miguel Sapochnik, who directed some of the most widely praised episodes of the flagship show.)
Some of the main players on House of the Dragon — D'Arcy, Considine, Matt Smith (Prince Daemon Targaryen), Olivia Cooke (Alicent Hightower), Rhys Ifans (Otto Hightower), Steve Toussaint (Lord Corlys Velaryon), and Eve Best (Princess Rhaenys Targaryen) — grace EW's latest digital cover, which gives an exclusive look inside the first Game of Thrones successor show.
"Time for Dragons!!!" McTavish had tweeted when the official poster for House of the Dragon arrived in June. "So excited to be part of this show and to share it with everyone very soon."
House of the Dragon premieres on HBO this Aug. 21.