Winter comes to Game of Thrones but for spin-offs, will it be springtime?

The network has teamed up with four writers to develop four potential spin-offs to Game of Thrones, telling new tales within the world created by George RR Martin

Lena Headey and Nikolaj Coster-Waldau in Game of Thrones. Helen Sloan / HBO / OSN

Last night, the first-to-last season of Game of Thrones premièred on HBO as devoted fans gleefully embraced the return of favourite characters, gruesome violence, and the series signature spider web of political intrigue. The houses of Westeros are still going at it — at least for now, anyway.

Next summer will be the final season. And then it will end. Forever.

Game of Thrones is HBO's flagship show and most-watched franchise — it's provided crucial ammunition for the premium network's escalating battle with streaming competitors such as Netflix and Amazon. But with the end in sight, it's an open question whether HBO can gin up a comparable replacement for a brand that garnered 8.9 million viewers for last season's finale.

HBO has a plan, and the plan is more Thrones. The network has teamed up with four writers to develop four potential heirs to the mother ship, telling new tales within the world created by George R.R. Martin. HBO President of Programming Casey Bloys said in an interview with the Hollywood Reporter last week that he hopes to get at least one spin-off out of the effort. They will be prequels with new characters, rather than reusing existing ones from the current show.

"It would be insane — with a universe like George has created that is so vast and has so many characters and so many timelines — to not, at least, entertain the idea, which is what we're doing," Bloys told the Reporter. A spokesman for HBO declined to comment further on the company's plans for Game of Thrones.

The franchise is working with two sets of canon — Martin's original works, called A Song of Ice and Fire, and the Game of Thrones show itself. Martin has written five of the seven planned novels in the saga. The two sides coexist much like Marvel's parallel universes in movies and comic books. HBO has much to draw on if it decides to use existing material for new shows. Official canonical sources include a set of six novellas written by Martin.

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Then there are the companion compendiums that detail the fictional world Martin created, including places that haven't been seen at all on the show. For instance, Martin's Lands of Ice and Fire, a boxed collection of twelve maps illustrated by a cartographer, depicts the known world and teases intriguing locales that fans may be interested in visiting. HBO declined to elaborate on how it will deal with canonical sources. Bloys said Martin himself is co-writing two of the potential successor shows.

So much has already been built. Histories, family lines, the cultures of peoples all over Martin’s fictional world — it’s all there for use in new shows. Take Daenarys Targaryen — you know, the queen with the dragons who’s played by Emilia Clarke. Dozens of characters we never see in the books or the show exist in the historical anthology, each with their own life story and personality. Plenty of deep-in-the-weeds fans are sure to love seeing what her forebears got up to — say watching Daeron Targaryen quell a rebellion or Jaehaerys Targaryen dispatching an army to the Free Cities.

It's almost impossible to create a universe alone, and those who found themselves in a situation like the one faced by Martin sought help. George Lucas opened up the Star Wars universe early on, allowing legions of writers to build what was called the "Expanded Universe," a massive library of novels, short stories, video games, and source books.

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Since acquiring Lucasfilm Ltd. in 2012, however, Disney has restructured how Star Wars content is made, culling the canon in favour of a rebuild. New books and shows are overseen by Disney and tie in to the main storyline of its feature films.

The strategy is part of a larger effort by the corporate home of Mickey Mouse. Both Star Wars and Marvel are being harvested not just for sequels, spin-offs, and everything in between, but for merchandising (of course) and ultimately the integration of everything into one huge entertainment platform. Sure, there are the billion-dollar films, but there are also toy Millennium Falcons for your kids and Darth Vader spatulas for your kitchen. There's even an immersive Star Wars hotel coming to a resort in Orlando.

Game of Thrones, with its vast universe and massive stable of characters, will be HBO's attempt at recreating such franchise magic. Granted, it also has a bench of young, non-Thrones fantasy in its line-up: Westworld, a show about a futuristic amusement park, had a successful first season. A series called Watchmen, based on the comics, is getting a lot of hype in its early development stage.

For now, though, the network is staying focused on the final two seasons of Thrones. It remains a mystery how the series will conclude, which faction will prevail, or whether the frozen undead from beyond the wall will simply kill everyone. But in the end, it's pretty fair to say without being a spoiler that, when it comes to raking in the cash, HBO will be sitting pretty on the Iron Throne.

* Bloomberg