“Game of Thrones” will return for its long-awaited eighth and final season in April, HBO announced on Tuesday.

The season will consist of six oversized episodes that will wrap up the sprawling tale and bring an end to one of the most popular shows in the world and HBO’s biggest hit in its history.

But the “Game of Thrones” franchise may just be getting started. At least one prequel series is in the works, created by George R.R. Martin, the master of the “Thrones” universe, and the writer Jane Goldman (“Kingsman: The Secret Service”). HBO has begun casting the show, set thousands of years before the “Game of Thrones,” with Naomi Watts signing on for an as yet undisclosed role.

Martin initially said the show would be called “The Long Night,” but has since revealed that the project officially remains untitled. (“The Long Night” is his preferred title, however.)

The promotional run-up to the final season of “Thrones,” and coverage of it, has already begun. On Tuesday, HBO released a teaser compilation that includes no footage from the new season but outlines the stakes for the final clash.

The clip kicks off a robust marketing campaign HBO has labeled #ForTheThrone that will “showcase the extremes the show’s characters have gone through in their quest for the Iron Throne,” HBO said in an announcement. The effort is designed to encourage fans to rewatch the previous seasons and convince the last remaining holdouts to catch up before the final season begins.

On Nov. 27, HBO will debut an enormous “Game of Thrones” promotion in Grand Central Station that will include a limited-edition run of 250,000 themed MetroCards.