Out of all gaming genres, horror is the one that few would directly associate with Nintendo. After all, its flagship titles largely use brilliantly chirpy and loveable characters in settings that maintain a family-friendly approach and mass appeal. But throughout its history, Nintendo has never been one to shy away from experimentation. And whilst the range of "mature" titles on GameCube was undeniably slim, a few games aimed to satisfy the craving for nightmares in the hearts of many a horror fan. One title in particular opened the darkened doors of phantasm beyond the usual horror fare, broke all the rules, and influenced the industry for years to come. That game was Eternal Darkness: Sanity's Requiem.

Developed by Canadian studio Silicon Knights and published by Nintendo, Eternal Darkness was released in 2002, showcasing a unique approach to horror gaming. It contained a narrative which required you to play as twelve different protagonists through two thousand years of history, each with their own story connected to the over-arching narrative of main character Alexandra Roivas. Alongside this were puzzles, a limb-specific targeting attack system, spellcasting, and a game-changing sanity gauge that created a myriad of hallucinations and illusions for players as it depleted. Layered on top was a richly dark atmosphere, drenched in the echoes of horror masters Poe and Lovecraft, with themes of madness and magic being the order of the day.

And it seems the development process featured just as many moments of insanity. Ted Traver, a lead designer on the game, reveals that the origins of the project began in the mid-to-late nineties. "Nintendo's interest in Silicon Knights started way back when Blood Omen: Legacy of Kain was first shown at a long-past E3. Even back then Nintendo was considering the addition of mature content to their line-up. So in time their agents contacted ours and the development process began."

Silicon Knights and Nintendo originally planned the game for release on the Nintendo 64. Lead Artist Raffaele Ienco reveals the past tools of the trade: "We used 3DStudio Max for geometry construction and Photoshop for textures for the N64 development. It wasn't that complicated back then." He also gives us an insight into the more intuitive development approach. "On the N64, it was a 'create as you go and if it's cool it stays in' type of atmosphere, which I really enjoyed. Back then, everyone was able to contribute and good ideas were always embraced." Ienco gives an example of the open approach to development. "One of my ideas was the dream sequence at the beginning of the game where Alexandra is fighting a few zombies and is able to kill them, but always dies, waking up in bed unharmed. That was in response to a Nintendo producer's thought that he wanted to start killing monsters sooner, and that the story sequence at the beginning was a bit too long. I voiced the dream idea immediately and we went with it."

By the year 2000, a large amount of the N64 game had been developed and was even playable at trade shows. The game's release seemed imminent, but as the new millennium approached and support for the N64 was starting to wind down, a major decision was made by The Big N. "We were several months away from finishing the game when it was decided the whole thing would move over to the Nintendo GameCube." Ienco reveals. Although the decision to move the game to another system so late on in development might sound odd, Traver reveals the logical explanation for the transition. "I am pretty sure that at the time Nintendo was short on titles for the GameCube. Also, the cost for manufacturing the high capacity cartridges for Eternal Darkness was high compared to that of their proprietary disk." But of course, this decision took its toll on the team. "The transition was brutal, and I really would not want to diminish any of the pain that staff members went through," continues Traver. "We had to make a new rendering engine, new background and character art, new animation, new sound, new tools, new pipeline. Pretty much everything had to be redone, and it pushed us all to our limits to finish it."

However, Ienco is keen to put a positive spin on the end result. "A lot of work was tossed out, but you could say the N64 version was the test run for the final one as a lot of things were improved on when we moved over to the GameCube." He goes on to explain the more technical aspects. "I remember we were allowed 4000 polygons for an environment on the N64 and that changed to 8000 on the GameCube and we had more texture allowance too. We were also developing a great camera system on the N64 and that continued onto the GameCube." But despite the improvements, he wishes that Silicon Knights had been a little quicker finishing titles. "It's a shame we didn't crank out more games for the N64 sooner and faster as we missed a great opportunity I think. I remember an Activision rep coming to the studio and seeing Eternal Darkness on the N64 and saying 'Wow! This game will sell 3 million copies!' It could have done on the N64 if we had immediately finished it in time for that Christmas season."

It's no wonder that the transition was tough for Eternal Darkness, as it was anything but a regular horror game. The narrative was complex enough on its own, with the main premise focused on ancient Gods wanting to destroy humanity at the turn of the new millennium. The protagonists of the game play their part in trying to stop these Ancients by uncovering hidden secrets in the Tome of Eternal Darkness, a large book bound together with flesh and bone. Due to the playable characters belonging to a range of time periods and geographical locations, this not only meant re-creating a diverse range of environments, but also recreating the small details contained within those civilisations.

But of course, there is one aspect of the game that no one forgets: the sanity meter. When the player encounters the many nightmarish monstrosities in the game, the meter depletes. To simulate the descent into madness, Silicon Knights threw in dozens of sanity effects that caused auditory and visual hallucinations during play. These included hearing whispers and blood dripping from the walls, but there were some brilliant fourth-wall-breaking effects too; one of the most notorious was the game claiming that your save data had been deleted. But what was the origin of such a mechanic?

"The sanity system came as an idea from a pen and paper role playing game: Call of Cthulhu by Chaosium Inc.," Traver reveals. "The sanity effects system and integration with all other game systems was planned from the start, but we had to figure out a way to make it work within our systems. It had to be clear to the player what was going on when we played tricks with them such as hallucinations, and false events like formatting the memory card." And although the concept is simple enough in principle, implementing the system was anything but. "Most of the sanity effects were handed by the code department. It was difficult stuff as many of the hallucinations had a variety of conditions required before they would trigger." And whilst these aspects of game design were nothing short of genius, Traver tells us of the struggle to get some of these ideas approved by Nintendo. "Getting Nintendo to sign off on game elements that conflicted with their certification process was difficult. They were worried about actual damage occurring to the card due to user intervention of yanking it out, worried that they had done something wrong."

Even so, Nintendo went with Silicon Knights's unorthodox approach, and the GameCube version of Eternal Darkness was nearing completion in late 2001, aiming for the launch of the console to coincide with its release. But then a world-shattering event occurred: the terrorist attacks on September 11th in the U.S.A. This seemingly unrelated event ended up having a substantial impact on the game's released form. In both the N64 and early GameCube footage, one of the most notable absences from the final version is a character called Joseph De Molay, a Templar Knight. A brief look at history sees that the Templar knights are well known for taking part in the Crusades, which sought to gain Christian control of particular holy locations in the Middle East. Understandably, Silicon Knights and Nintendo thought it best to remove Joseph from the game, with some story elements and locations also seeing revision. "We were able to keep all the Middle Eastern environments, but we had the Templar Knight character changed to an oil-well fire-fighter instead." Ienco explains. "Any game textures that had Arab writing had to be removed from the game. Everyone was scared of giving offence and being attacked for it by terrorists, almost to an extreme."

Nevertheless, development continued, with Nintendo lending a hand during the homestretch. "Near the end of development on the GameCube version of Eternal Darkness, two of Nintendo's premiere designers 'parachuted' into Silicon Knights's headquarters and did nearly a full top-down 'fix' of the Eternal Darkness design gameplay, improving it substantially," recalls Ienco. "Some designers recognized their value to the benefit of the game; others felt some bitterness and frustration that they were side-lined, as the improvements were made without any need of their further input." However, Traver looks back on Nintendo's involvement positively. "I personally believe that Nintendo helped us in a great many ways to create the best product we could at the time."

Unfortunately, Eternal Darkness did not become the monster hit many hoped it would be when released in 2002. Ienco reinforces his belief that the game would have gained a better reception on N64. "The PlayStation 2 and original Xbox were too overwhelming to consumers and we were lost in all the new games." Even though it underperformed sales wise, Eternal Darkness received wide critical acclaim and great appreciation from fans. And whilst it wasn't the first game to play with the idea of breaking the fourth wall, it made it an integral part of the experience throughout and its influence is still being seen in the industry today in titles ranging from the Batman: Arkham series to modern horror greats like Amnesia: The Dark Descent.

But after thirteen years people still talk about the idea of a sequel, with Nintendo currently holding the rights to the original IP (as well as a patent for the sanity meter filed in 2005). However, many have claimed and speculated that work began on a sequel soon after the game's release. We asked Traver whether a sequel was proposed for development back in the day. "Yes, just as Too Human prototypes were being worked on during the development of Metal Gear Solid: Twin Snakes." But Traver quickly points out the project didn't progress far. "Development can occur on many levels. In the case of 'Shadows' it was mostly talk and a few corporate overviews for tendering to Nintendo. It didn't go any further than that as far as my recollection."

However, there is another possible future of the game; one that is tied to the bizarre fate of Silicon Knights. After the closure of the studio, Denis Dyack (Eternal Darkness director and founder of Silicon Knights) set up Precursor Games in 2013 and unveiled a crowdfunding campaign for a spiritual successor called Shadow of the Eternals. After two failed crowdfunding attempts, Precursor Games was closed and Dyack then set up a multimedia developer called Quantum Entanglement Entertainment in 2014, insisting the game would continue development. Whether Shadows of the Eternals does get released remains to be seen, but the back and forth nature of the spiritual sequel and different studios seems to tie-in with the suggestion that Silicon Knights had a strange culture of starting and stopping. As Traver explains, "Silicon Knights had a bad habit of starting on new ideas before the current ones were finished, splitting resources and focus, as well as creating division within the team itself." Although the nature of any sort of follow up is questionable, there's no doubt it would capture much interest. And it doesn't change the fact that Eternal Darkness is a great horror classic which is still underappreciated, especially when considering the ideas it set in motion. Never seeing any sort of re-release, the only physical copies of the finished game are on GameCube.

Whilst fans speculate about the existence of finding an in-progress N64 cartridge of the game, there is one treasure that few fans still don't know about: the Eternal Darkness game design document. "The game design document was probably one of the best ones we ever made, with the final version being printed out to look like an old tome, with the thickness of a phone book." Traver proudly proclaims. "Every director and lead got one so there were quite a few printed." Although Traver doesn't have his anymore, some of them are still in existence. "I still have mine." Ienco states. "90% of the art inside is mine, so of course I kept a copy somewhere. I haven't seen it around here for a decade though!"

If you haven't played Eternal Darkness, then find a copy for this Halloween, turn off the lights and experience one of the most unique titles on any Nintendo console. And for those who enjoy hunting rare gaming treasures, keep an eye out for those game design document tomes. For they, like the titular Tome of Eternal Darkness, would surely reveal a history of hidden secrets.

A huge thanks goes to Ted Traver and Raffaele Ienco for their time and resources. Raffaele is currently anticipating the release of his new science fiction comic Symmetry in December, released by Image Comics.