In Guerrilla Games' Horizon Forbidden West, players are given the opportunity to dive into what are called "Cauldrons." In the world of the game, they're automated factories that create many of the machine creatures that populate the world. In the core gameplay loop, they're meant to be fun standalone levels that reward players by unlocking the ability to turn machines from friend to foe.
These Cauldrons usually aren't located on the game's critical path, but still receive an incredible amount of time and attention from Guerrilla Games' level design team. In Forbidden West, one of these Cauldrons (Cauldron IOTA) climaxes with the player riding the head of a Tallneck as it emerges from the Cauldron. It's an incredible moment that's unlike any other in the game, and it manages to beautifully weave the game's story, gameplay, and visual power all into one memorable beat.
At GDC 2023 level designer Dennis Micka broke down his process for designing this particular Cauldron, and how he had to make a lot of mistakes on the way to the finish line.
Horizon Forbidden West's Cauldron IOTA was meant to "break the rules" of Cauldron design
Micka began his talk with an explanation of how the team at Guerrilla approached Cauldron design when making Forbidden West. In the previous game, Horizon Zero Dawn, all Cauldrons had a generally familiar flow. Players discovered the entrance to the Cauldron, navigated to its core, fought a boss, then exited with their new powers.
That is, except for Cauldron Xi, which flips that level flow on its head. First, players navigate the Cauldron and fight human enemies instead of machines. Then they activate the core, and have to then backtrack the way they came, fighting reactivated machines that are also battling the same humans the player fought on the way in.
Micka said this was one of the most "memorable" cauldrons of Zero Dawn, and that players enjoyed the shake-up in format. It became one of his inspirations for designing the cauldrons of Horizon Forbidden West.
Though that inspiration was key to making new Cauldrons, there were still lots of other lessons Micka had to learn while shipping the cauldrons of Forbidden West. The first of these came from designing Forbidden West's first Cauldron: Cauldron MU.
Cauldron MU was, for a number of reasons, required to follow conventional Cauldron design flow. Micka and the team were able to use some new mechanics like player character Aloy's glider when designing the level, but otherwise the space had to be able to introduce new Horizon players to how Cauldrons work, and help re-familiarize returning players on the same concepts.
This Cauldron also allowed Micka to learn some key early lessons that would make his other Cauldrons better. First, he ultimately viewed the area as "too large," "too disorienting," and filled with combat spaces that were too small.
The space was "too cramped" with a number of small setpieces. Players sometimes got lost or confused, and the space looped in strange and confusing ways.
Cauldron IOTA would be a physically smaller Cauldron, but Aloy would need a similar amount of time to navigate it. Players would make their way in through a side entrance to the structure and discover that the Cauldron was designed to assemble Tallnecks—the gigantic Machines that Aloy can climb to unveil huge sections of the map. They're docile, majestic beings and Micka said this level was inspired by the companionship players are able to achieve with some machines.
When players enter the space, they find that the Tallneck assembly process has been interrupted, and they will need to restart the process to activate the core and exit the Cauldron.
Though the final setpiece was clear for the start, the level needed some key motivating elements. Though the idea of repairing a Tallneck is cool, the world of Horizon doesn't fully motivate the player to take on these tasks. Cauldrons are meant to operate without human intervention, so the facility would need to have been halted somehow. Aloy isn't personally motivated to create new Machines, so she would have to have a direct narrative reason to.
And finally, how would Aloy get on top of the Tallneck as it exits the cauldron? This last step would require centering the Tallneck in Aloy's immediate goals.
Micka would later work with Horizon Forbidden West's narrative team to create these storytelling elements the Cauldron needed, but those questions influenced the objectives he'd have to construct to anchor player movement in the space. Ultimately, it was decided that the Cauldron would have been hijacked by a rogue AI called Hephaestus, and that Aloy's goal was to stop the production of violent Machines.
Micka hoped that because Tallnecks and Cauldrons are both beloved by players, pulling together this Cauldron would be a fairly smooth task. But to get to the finish line, he still had to cross some major hurdles.
Cauldron IOTA took some serious work
While Micka's first pitches for Cauldron IOTA were accepted by his superiors, he ran into trouble as he iterated on stages. First, designing a Tallneck-centered Cauldron came with massive technical challenges. Tallnecks don't enter combat, meaning that many technical solutions for breaking them, assembling them, or having them move on a vertical axis didn't exist.
This—and the general trials of game development—meant that the Cauldron was at risk of being cut, especially since internal playtesters were having trouble navigating the level. Fortunately for Micka, a number of developments helped him clear the obstacles.
Micka said that he took time away to work on another Cauldron—the overgrown Cauldron KAPPA. Here, he found that centering the Cauldron's design on multiple key setpieces helped smooth out the process, and that this area's development went relatively more smoothly.
By the time he returned to IOTA, another Tallneck setpiece and Cauldron had also been cut from the schedule. That left this Cauldron in a stronger position for final game inclusion.
As Micka smoothed out Cauldron IOTA's gameplay, he was able to figure out the lack of Tallneck tools with a mix of short hacks and assistance from the technical design team. Parts from the T-Rex-inspired Thunderjaw were swapped in where needed on the Cauldron assembly line, and the visual of the Tallneck being assembled was thrown out.
Instead, the assembly process would be "finished" every time players walked through a specific door, where the camera would center on the Tallneck's head being lowered onto the rest of the body. It was a decent hack for giving the illusion of an assembly process.
Finally, the technical design team helped create some specific features to let the Cauldron elevator carry the Tallneck to the surface with Aloy riding on top. The camera becomes locked in an upward position as the mechanical beast rises to the surface, and players get to see layers of opening metal grates that sell the drama of the moment.
The climax was all worth it. Players would rise back to the surface on the head of a mighty beast, treated to a beautiful view of the landscape, with new unlocked machine override powers in hand.
Last lessons from making Cauldron IOTA
Creating Cauldron IOTA taught Micka several key soft-skill lessons in the level design process. Sure, he was learning plenty of level design tricks in the process, but to make great art, you have to grow as a person too.
First, he urged attendees to use their pre-production time well. One key setpiece in Cauldron IOTA where players ride on the Tallneck's head as it moves to the assembly bay came from some experimenting in pre-production, where level and tech designers worked together to make a new batch of movable objects to sprinkle across the game.
Next, he reiterated the idea that "bigger doesn't equal better." Cauldron MU was big and impressive, but it wasn't as memorable as the more compact Cauldron IOTA.
Cauldron IOTA also crossed the finish line because Micka kept coworkers from other teams "involved" in the process. Colleagues in the technical design and art departments helped create the tools he needed to sell this big Tallneck moment.
And for level designers frustrated that their work isn't coming together, Micka urged them to keep the faith, take time to work on other levels, and not give in to imposter syndrome.
"Imposter syndrome is real, but don't let it get you down because everyone has had it at some point. And if they say they don't, they're lying," he quipped.
"It's alright to feel this way because you wouldn't be where you are if [your team] didn't trust you."