Word on the street is HBO's about to become the freaking Game of Thrones Prequel Network, but there's still only one we have any concrete information on. That'd be House of the Dragon, a series following in the fiery, incestuous dragon-riding family the Targaryens. Today, HBO added a few more names to the series' quickly-growing cast: Rhys Ifans (The Amazing Spider-Man), Steve Toussaint (It's a Sin), Eve Best (Nurse Jackie), and Sonoya Mizuno (Devs).

Ifans will play Otto Hightower, Hand of the King to King Viserys Targaryen. Toussaint joins the series as Lord Corlys Velaryon, better known as The Sea Snake, "the most famed nautical adventurer in the history of Westeros." Best will portray his wife, Princess Rhaenys Velaryon, a dragonrider who was "passed over as heir to the throne at the Great Council because the realm favored her cousin, Viserys, simply for being male." Mizuno rounds out the cast as Mysaria, whose official character description is:

"Mysaria came to Westeros with nothing and has been sold more times than she can recall. She could have wilted… but instead she rose to become the most trusted — and most unlikely — ally of Prince Daemon Targaryen, the heir to the throne."

The recently-announced castmembers join Matt Smith, Olivia Cooke, Paddy Considine, and Emmy D'Arcy. House of the Dragon, which is set 300 years before Game of Thrones, was co-created by A Song of Ice and Fire author George R.R. Martin and Ryan Condal, the latter of which wrote the pilot. According to HBO head honcho Casey Bloys, the series starts production in April. For more on House of the Dragon, here are a few details on the return of GOT composer, Ramin Djawadi.