How The Rings of Power episode 6's explosive ending was brought to life

Full spoilers for The Rings of Power episode 6 follow. You've been warned.

The Rings of Power has officially arrived. Sure, the high fantasy Prime Video show actually launched on September 2, but it's needed a hugely significant episode to truly announce itself on the prestige TV stage.

Episode 6 is the epic and explosive entry Amazon's Lord of the Rings TV series and audiences have been waiting for. It's packed with frenetic and fraught set-pieces, tells a story with multiple twists and turns, and culminates in a stunning finale that'll have viewers' jaws on the floor long after the credits roll.

Unsurprisingly, a lot of work went into designing and crafting episode 6's shock ending. And, as co-showrunners Patrick McKay and J.D. Payne told TechRadar at an exclusive preview screening, the episode's final moments were planned as season 1's tentpole moment as far back as 2018.

"[It took] four years," McKay says. "We've known about that sequence for that long."

"When we were blocking out season 1, we had a whiteboard of character arcs for Galadriel, Elendil, Isildur, Arondir, Bronwyn – all the main characters in this episode," Payne adds. "All of those journeys were leading to this point when we finally introduce Mordor."

That's right, The Rings of Power episode 6 shows us how Mordor – and its iconic volcano, aka Mount Doom – were ultimately created. 

Viewers had already speculated that Mordor's introduction wasn't too far away, with previous season 1 episodes teasing as much. In episode 3, Galadriel and Elendil pour over some old Middle-earth maps, which show that the region known as the Southlands sits right on top of where Mordor exists in J.R.R. Tolkien's Hobbit and Lord of the Rings novels. Adar's orc army is based in this location throughout season 1 – an area where they've dug tunnels and deforested large swathes of land – which had lent further proof to Mordor's eventual arrival.

What audiences didn't expect is that Mordor and Mount Doom would be born this early in the series. However, those familiar with Lord of the Rings' extensive history would've been able to work out that this iconic location would be part of episode 6. Its official title – Udûn – is also the name of a barren valley situated in northwest Mordor, so it wouldn't have taken much for diehard Tolkien fans to make the connection.

Still, for casual Lord of the Rings fans and general audiences, the birth of Mordor and Mount Doom in The Rings of Power is a truly shocking and visually spectacular moment. So, how was the sequence developed?

The eruption of an idea

Udûn's finale was a seismic undertaking for everyone involved in The Rings of Power. The explosive sequence's final edit comprises multiple VFX shots, complete with a huge volcanic eruption, searingly hot rocks raining down from the sky, a storm-fuelled ash cloud, and fires breaking out as the Southlands and its inhabitants are consumed by the cataclysmic event.

Before its visually arresting effects could be added in post, The Rings of Power's chief creative team had to make sure that events preceding the eruption could lead to the mountain – that becomes Mount Doom – violently blowing its top. After all, such a move is only possible via the collision of its vast lava pit with water from Ostilith's deep reservoir. That happens after Southland turncoat Waldreg uses the sword hilt, which Adar reacquires from the Southlanders in episode 6, as a key to unlock part of Ostilith's dam. It's a move that allows a deluge of water to rush through numerous tunnels – dug by the orcs – and snake its way to the ice covered mountain, which becomes Mount Doom.

Could a combination of an expansive volume of water and a giant pool of lava, then, cause such an explosive eruption? According to real-world science, yes.

"One of our writers knows a geologist," Payne explains. "So we asked them if water and lava could unite to create this gigantic explosion, and it could. They said 'if you have enough steam pressure that builds up in a confined space, the entropy inside the volcano will increase, eventually causing it to blow."

"We painstakingly studied what actually happens in volcanic eruptions," VFX producer Ron Ames adds. "We looked at photographs and we read historical documents on Pompeii so we had a clearer idea of the scale of these naturally occurring explosions."

Buoyed by the backing of real-life science, The Rings of Power's huge crew set about creating a finale that would herald the show's epic arrival on the world stage. Typical pre-production work, such as concept art, storyboards, and location scouting were carried out well in advance of principal photography. Once those elements were in place, multiple camera crews set out to film external shots – wide and sweeping landscape, as well as close-ups – to use during the sequence.

"It was important to us to use real world locations," Ames reveals. "The actual mountain itself is based on a real location. The cliff that Ostilith sits on is an actual location. We went to those areas and shot backgrounds using helicopters. We also landed in those areas and took photographs and plates. Even the water you see in the final sequence is real – it's just mixed in with some CGI elements to aid the flow of this massive deluge as it careens down the valley."

Heating up in post

With pre-production and principal photography in the can, the lengthy post-production process could begin.

Like many of The Rings of Power's VFX-laden sequences, episode 6's finale was developed by multiple animation studios. Weta Digital, who worked on Peter Jackson's Hobbit and Lord of the Rings movie trilogies, produced the Ostilith cliffside-based portion. Lucasfilm's Industrial Light and Magic (ILM) crafted the underground sequence, which leads to the violent explosion. Meanwhile, Australian-based studio Rising Sun were tasked with creating the post-eruption scene, including the spewed lava rocks and rapidly traveling ash cloud.

"Once all the vendors mixed each part together, you can't tell where one shot starts and another ends," Ames says. "It's all seamlessly connected and I couldn't be more proud of the teams that worked together to compose and knit it together. It's one of my favorite sequences in the whole show."

Crunching has become a hot topic of conversation in the film and TV industries, with big-budget projects – including She-Hulk: Attorney at Law on Disney Plus – and studios coming under fire over employees' working conditions.

Given the scale of this sequence and 9,500 other VFX-based shots in season 1, it seems inevitable that The Rings of Power's backstage crew would have to crunch at some point. Ames, though, was adamant that no one under his supervision would be forced to work longer – at the cost of their physical and mental wellbeing – to ensure sequences like the Mount Doom one were completed in time.

"Having seen the film business change and being an advocate for technology, I would say mindfulness and and an approach to sharing the load is extremely important," Ames says. "Largely, we didn't work more than 12-hour days. In some instances, I had to send crew members home to sleep and shower – they all worked extremely hard, but everyone got to go home, to see their families, to attend weddings, and do all the things humans need to do. I think the future of filmmaking requires us to look at mindfulness in the workplace and how to move forward in a balanced way to get the most creativity out of our artists."

Udûn's final sequence is a visually striking sight to behold. It's the brainchild of multiple creators and studios, all of whom worked diligently to collaborate on The Rings of Power's most harrowing spectacle to date. "It was ILM VFX supervisor Jason Smith's creation," Ames says, but the countless artists, animators, renderers, and other crew members deserve as much praise for creating such a devastatingly beautiful moment in Middle-earth's history.

With two more episodes to come in season 1 – not to mention four more seasons' worth of storytelling to come – The Rings of Power will contain more shocking, big-budget sequences like episode 6's finale. Right now, though, Udûn is the explosive show-defining entry that the Prime Video series required – and it'll take something truly amazing to usurp it.

The Rings of Power's first six episodes are available to stream on Prime Video now.