It's been three long years since Jon Snow broke the wheel in the final episode of Game of Thrones. In HBO's House of the Dragon, which debuts on Aug. 21, we return to Westeros. There's no doubt Game of Thrones lost some of its luster during its final two seasons, but House of the Dragon could be one of the year's TV highlights if it reclaims some of that Thrones' magic.

We know quite a bit about the upcoming blockbuster series. It was expensive, costing around $20 million per episode according to Variety, which is appropriate. After all, Game of Thrones became famous for bringing Hollywood production values to your living room. We also know that it's a prequel. Fans hoping to once again see Ned Stark or Tyrion Lannister will end up disappointed, as House of the Dragon is set 200 years prior to the murder of Jon Arryn that precipitated eight seasons of chaos.

 Here's what you need to know before watching HBO's Game of Thrones prequel.

What is House of the Dragon about?

House of the Dragon is about the Targaryen family, who ruled Westeros for 300 years. House of the Dragon begins around 100 years into House Targaryen's reign.

Viewers of Game of Thrones know the Targaryen dynasty effectually ended with Robert's Rebellion, a civil war that saw Robert Baratheon succeed "The Mad King" Aerys Targaryen as Ruler of the Seven Kingdoms. By the time Game of Thrones begins, 17 years after the Rebellion, there are only two known Targaryens: Daenerys and Viserys. In Game of Thrones, the Targaryens were a formerly great House. In House of the Dragons, we get to see them as the great House. 

At least, for a while. 

House of the Dragon depicts the beginning of the end for the Targaryens. It follows what in A Song of Ice and Fire lore is called the Dance of the Dragons -- a civil war that erupts after two Targaryens voice countering claims to the Iron Throne. King Viserys raised his daughter, Rhaenyra Targaryen, to succeed him, but after Viserys' death, it's Viserys' eldest son to his second wife, Aegon, who gets crowned the new ruler.

That kicks off a war that sees many a dragon slain, and many a Targaryen killed.  

Is it based on a George R.R. Martin book?

Yes. George R.R. Martin, seemingly on an unending quest to procrastinate writing Winds of Winter, released a book called Fire and Blood. It's a fictional history book that chronicles House Targaryen. 

Ryan Condal and Miguel Sapochnik, showrunners for House of the Dragon, recently told IGN the show would differ in some ways to the book.

"The fun of this show is that it plays as a bit of a companion piece to the history book," Condal said. "It communicates with the history book. In a sense that, some things will line up. Other things will be told very differently. But the idea is that, in the end, the events are the same. It's just the 'why' and 'how' they happened that changes as you see the actual history."  

In an interview with SFX, Condal said the show is "like Succession, [but] with dragons."

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Who's running the show?

As noted, Condal and Sapochnik are showrunners for House of the Dragon. That makes them the rough equivalents to David Benioff and D.B. Weiss, who gained great fame (and, later, criticism) for their roles as Game of Thrones showrunners.

Condal is credited as House of the Dragon's creator. Prior to the HBO epic, Condal wrote the screenplays for Hercules and Rampage, both starring Dwayne "The Rock" Johnson. 

Sapochnik is a name known to diehard Game of Thrones fans, as he directed several of the show's most celebrated episodes. That includes Season 5's Hardhome and Season 6's Battle of the Bastards. 

As an aside, Game of Thrones composer Ramin Djawadi is returning to write House of the Dragon's score. That has nothing to do with the show's creative but is worth mentioning -- because the Game of Thrones score ruled. 

Is House of the Dragon the only Game of Thrones prequel?

It is now! There were originally two planned Game of Thrones prequels. The other, set to star Naomi Watts, was to take place 1,000 years before the events of Game of Thrones.

If you've got an insatiable fix for all things Fire and Ice, your best bet, besides House of the Dragon, is the perennially delayed Winds of Winter. That's the sixth book in the series, one that Martin has been writing since 2011. Martin is also going to write a second volume of Fire and Blood, but not until after he completes .Winds of Winter, according to a July blog

House of the Dragon debuts on HBO and HBO Max on Aug. 21.