Amazon has officially greenlit one show that it hopes to rule them all.

The company has made a multi-season production commitment to a television adaptation of J.R.R. Tolkien’s fantasy epic The Lord of the Rings.

It’s a major deal securing one of the biggest brands in pop culture for what’s likely to be one of the most expensive TV shows ever made.

But there’s a catch, creatively speaking: The series will explore storylines set before the events in the first LOTR novel, The Fellowship of the Ring. In other words: The war to destroy the One Ring as chronicled in Peter Jackson’s Oscar-winning trilogy of films will not be told in the TV version. So this story is either set before The Hobbit or in between The Hobbit and LOTR.

This something we’ve seen with other recent TV series when they tackle major cinematic titles with certain rights restrictions. Like how Fox’s Gotham can tell the story of young Bruce Wayne but not Batman, how FX’s Legion has avoided using the term “X-Men” even though its an X-Men project, or how Syfy’s upcoming series based on The Purge films will be set in between actual Purges.

Amazon’s deal includes a potential addition of a spin-off series as well.

“We are delighted that Amazon, with its longstanding commitment to literature, is the home of the first-ever multi-season television series for The Lord of the Rings,” said Matt Galsor, a representative for the Tolkien Estate and Trust and HarperCollins. “Sharon and the team at Amazon Studios have exceptional ideas to bring to the screen previously unexplored stories based on J.R.R. Tolkien’s original writings.”

There’s no cast or premiere date yet, but the series will eventually stream on Amazon Prime.

The move by Amazon comes as HBO prepares to conclude its mammoth fantasy hit Game of Thrones, which will almost certainly premiere its final six episodes in 2019. HBO is developing multiple potential prequel series based on author George R.R. Martin’s Westerosi history, though none are guaranteed to air.

In a way, Amazon’s LOTR project and HBO’s GoT prequels face the exact same challenge: The great high-stakes story and beloved characters that made each tale such a classic will have already been told — and both benefited from mining a fantasy author’s years of extraordinary effort producing more than a thousand pages of intricate creative storytelling. So can a network find writers who can successfully bootstrap a relatively new-ish story set in these familiar fantasy worlds that capture at least some percentage of the original work’s worldwide appeal?

It’s a tough call as to which company has the more difficult task. For Amazon, the stakes are rather low (the company’s stock is trading at an incredible $1,138 per share). For HBO, the stakes are very high — GoT is an unprecedented massive moneymaker for the network and a creating subscription-worthy TV is its core business (while fending off the likes of Netflix and Amazon). But HBO has a distinct creative advantage in that they’re developing five potential prequels while committing to none in advance — so the network has several chances to find a story that really works before deciding on a path. This new deal struck between the Tolkien Estate and Tolkien Estate and HarperCollins, however, locks Amazon into a multi-year series commitment without so much as a writer yet hired — that’s the type of deal that keeps a traditional network up at night though, again, Amazon can afford the write-off if it all goes south.