• HBO is expanding the "Game of Thrones" universe with another prequel.
• "A Knight of the Seven Kingdoms" takes place between the main series and "House of the Dragon."
• It's based on George R. R. Martin's novellas and follows a knight and his squire.

"House of the Dragon" season three probably won't air until 2026, but "Game of Thrones" fans have another prequel to look forward to in the meantime: "A Knight of the Seven Kingdoms."

Although the "Game of Thrones" ending disappointed many fans in 2019, HBO recognized that the world of Westeros is a lucrative property. And there's plenty of material to use considering all the spinoff stories and novellas that George R. R. Martin has written.

The network is also working on other "GOT" prequel shows, including "Nine Voyages," "Ten Thousand Voyages," and "The Golden Empire."

"A Knight of the Seven Kingdoms" is set about 70 years after "House of the Dragon" and 100 years before "Game of Thrones," as the network fills in the huge timeline of the fantasy franchise.

The story follows Ser Duncan the Tall and his squire, Egg. Here's what you need to know about "A Knight of the Seven Kingdoms."

'A Knight of the Seven Kingdoms' is about Dunk and Egg

The first season is based on Martin's first novella in the "Tales of Dunk and Egg" series, which is called "The Hedge Knight."

It introduces Ser Duncan the Tall, a knight who roams the country offering his services. At a tournament to prove his knightly skill, Duncan meets a boy with a shaved head called Egg.

Egg's real name is Aegon Targaryen, a distant member of the feared rulers of Westeros.

The series depicts his youth away from the centers of power — but later in his life, he bypasses many in the line of succession to be crowned Aegon V and take the Iron Throne.

After "The Hedge Knight," the unlikely duo's adventures continue in "The Sworn Sword" and "The Mystery Knight."

In May 2023, HBO executive Francesca Orsi told Deadline that the network plans to adapt each of the three novellas into a six-episode season.

But, as with the source material for "Game of Thrones," Martin has not finished Dunk and Egg's story. In a 2015 blog post, the writer said he plans to write more Dunk and Egg stories, with tentative titles including: "The She-Wolves of Winterfell," "The Village Hero," "The Sellsword," "The Champion," "The Kingsguard," and "The Lord Commander."

Should Martin release these in the future, HBO could easily turn "A Knight of the Seven Kingdoms" into a longer-running series.

'A Knight of the Seven Kingdoms' will premiere in late 2025

In March 2024, Warner Bros. CEO David Zaslav confirmed to investors that "A Knight of the Seven Kingdoms" would start streaming on Max in "late 2025," IGN reported.

Warner Bros. Discovery's head of global streaming and games, JB Perrette, said that the "late 2025" launch was still a go, Variety reported in December. The publication indicated that, according to its sources, the series would likely premiere in the fourth quarter of 2025 — i.e. sometime in October, November, or December.

The 'Knight of the Seven Kingdoms' cast is led by Peter Claffey and Dexter Sol Ansell

"A Knight of the Seven Kingdoms" stars Peter Claffey ("Bad Sisters") as Ser Duncan the Tall, and Dexter Sol Ansell ("The Hunger Games: The Ballad of Songbirds & Snakes") as Egg, his young squire.

In June 2024, HBO announced that five other actors had joined the cast, per Deadline. "True Detective: Night Country" star Finn Bennett will play Prince Aerion Targaryen, "The Gentlemen" actor Daniel Ings will play Ser Lyonel Baratheon," and "Fargo" season five star Sam Spruell will play Aerion's father, Maekar Targaryen.

Additionally, "The Crown" alum Bertie Cavel will play Maekar's brother, Baelor Targaryen, and Tanzyn Crawford will play Dunk's love interest, Tanselle.

In August, Entertainment Weekly reported several more actors had joined the cast of the prequel, including "A Good Girl's Guide to Murder" star Henry Ashton as Daeron Targaryen.

He isn't the same Daeron who gets mentioned in "House of the Dragon," because "A Knight of the Seven Kingdoms" is set 100 years later — the Targaryens often reuse names.

Ashton will be joined by Edward Ashley as Ser Steffon Fossoway, Daniel Monks as Ser Manfred Dondarrion, Youssef Kerkour as Steely Pate, Tom Vaughan-Lawlor as Plummer, Shaun Thomas as Raymun Fossoway, and Danny Webb as Ser Arlan of Pennytree

The first trailer for 'A Knight of the Seven Kingdoms' showcased Dunk and Egg

HBO released the first teaser for "A Knight of the Seven Kingdoms" as part of a 2024-2025 preview trailer in August 2024, alongside footage from other highly anticipated shows including "The Penguin," "IT: Welcome to Derry," and "The Last of Us" season two.

The footage sees Dunk introduce himself as Ser Duncan the Tall while also giving a brief look at Egg. There are a few quick shots of Dunk training with his sword and a moment where he punches someone during a fight.