- "Each Vault's knowledge was transmitted to a single place."
- ―Jupiter speaking of the Grand Temple.[src]
Like the other temples across the planet, its purpose was to create different methods of saving and preserving the world; it was the location where Jupiter, Minerva and Juno collected and tested the discoveries of the other Temples in the hope of finding the most effective methods of Earth's salvation from the solar flare.
To maintain its operation, the Grand Temple was buried underground to protect its contents from the war with humanity and the solar flare, and was hidden beneath a statue dedicated to the Capitoline Triad. However, the statue was destroyed in the First Disaster, and its location remained a mystery until Desmond Miles' revelation.
It was also the place where Juno had been imprisoned, in order to protect the humans from her plots of destruction, and held the device that would both set her free and protect the Earth from the second solar flare.
Before and after the war with humanity, all information from the other Temples regarding any way to prevent the first catastrophe was sent there for Jupiter, Juno, and Minerva to "sort and sample all that was collected." The three tested six possible solutions in succession, "each more encouraging than the last", but all six solutions ultimately failed.
The first solution was to build four towers to collect the solar flare that would strike the planet, and virtually dispel it. While they had the means and resources, the time to produce the solution would take too long to be successful. The first tower was never completed and the research was abandoned.
However, Juno mentioned that some members of the First Civilization attempted to continue the pursuit of this solution, and sought to automate the construction process, hoping that the machines would have been able to finish the first tower.
The second solution was to use the Shards of Eden, on a much larger scale than ever before. The magnetic field emitted by the Shards could protect the planet against the solar flare, but it was too large to build and was considered impossible.
The scientists hoped to save a possible half, a sixth, an eighth, or even a tenth of the planet. However, the lack of time and resources proved too great, and it was theorized that a city might have been spared at best, given more time. Like the first solution, this one was also abandoned in the end.
The third solution was discovered by using the Apples of Eden to control humanity. If enough humans were compelled to believe in one idea, their thoughts took on form and became reality.
The consequent solution involved launching an Apple of Eden into orbit, aiming it towards the planet, and commanding the entire human race to think one thought, "Make us safe."
However, even with a dozen of the Apples sent into orbit, the First Civilization lacked the means to direct and maintain the control beam, and simultaneously influence the humans on a global scale. The project was eventually abandoned.
Minerva discovered that there was a pattern of numbers and equations that define existence. If one could comprehend these numbers, time itself could be tamed. The fourth solution was to attempt to go back in time and prevent the disaster before it could occur.
Unfortunately, it appeared that the scientists' attempts had no effect on the present. The device they created could, however, look into the future, to see if the other solutions would prevent the disaster, but the result was always a failure.
The solution was abandoned, though Minerva herself continued her studies on the underlying mathematics of the universe, and eventually used her knowledge to actively communicate with individuals in the far future, such as Desmond Miles, through the memories of his ancestor, Ezio Auditore da Firenze.
The fifth solution was to augment the bodies of the remaining First Civilization members to adapt into the hostile new climate which appeared on Earth following the catastrophe.
Aita, Juno's husband, volunteered to test the method, resulting in his mind degenerating and becoming increasingly catatonic. With enough will, he wished for Juno to euthanize him, and she fulfilled it. The solution was subsequently abandoned.
The sixth solution was to create entirely new vessels that could safely transfer one's consciousness in a way that the former solution had failed to do. The new vessels would be able to withstand the new environment, and they could house the transferred consciousness.
However, while transferring one's consciousness into the new vessel was easy, subsequent releasing of oneself from the vessel was nearly impossible, and required another being's sacrifice to be successful. As a result, this solution was ultimately abandoned.
Following this, the solar flare destroyed most of the First Civilization and left less than 10,000 humans alive. However, the two groups worked together, beginning around the remains of the Grand Temple. The members of the First Civilization attempted to pass on their gifts to humans through crossbreeding, resulting in some individuals being able to access Eagle Vision and use the Pieces of Eden.
The scientists determined a similar disaster would occur again in 2012. Minerva found a new solution from her research and created a pedestal, the Eye, that would allow one who had the right genetic material to manipulate the numbers to protect the Earth. However, before Minerva could test it, she discovered that Juno had tampered with it. While the patterns to save the world still existed, they would also allow Juno to have total control and power. As such, Minerva forced the solution to be abandoned, and Juno's consciousness was imprisoned in the Grand Temple.
Around 800 CE, the Kanien'kehá:ka settled near the Grand Temple. Using a Crystal Ball to communicate with Juno in the Nexus, who they believed was a "god", the villagers of Kanatahséton became the guardians of the "sanctuary", and their duties forced them to isolate themselves from the other Iroquois. Over time, the stories of the tribe's communications with Juno were painted on the Temple door, referring to her as a motherly figure who constantly watched over and protected the Kanien'kehá:ka.
Before leaving to wander the world and guide the humans, Minerva used the Eye to communicate with the Assassin Ezio Auditore da Firenze, a descendant of the First Civilization, in the Vatican Vault in 1499; unbeknownst to Ezio, his memories would be viewed by his descendant Desmond Miles in 2012 through the Animus.
Considering this, Minerva spoke directly to Desmond through Ezio, telling Desmond about her people, the war with humanity, the disaster, and their efforts to rebuild the world. She also warned Desmond to act quickly and to beware of "the cross", referring to the Templars.
In 1506, Ezio Auditore and Leonardo da Vinci discovered a smaller vault in Rome. Unlike the Vatican Vault, the Pythagorean Vault contained a set of coordinates: 43 39 19 N 75 27 42 W. Leonardo was baffled by the information, but Ezio inherently understood that these numbers were intended for Desmond.
William Miles, Desmond's father and the de facto Mentor of the Assassin Order, noted these memories outside the Animus, and set out to these coordinates, which he believed to be the location of another temple.
In 1511, Prince Ahmet, the Templar leader in Constantinople, desired the location of the Grand Temple in order to end the differences between men, and create a unified world. He believed that the legendary Assassin Altaïr Ibn-La'Ahad discovered the temple's location, and that he had hidden that knowledge in his library beneath Masyaf.
With this belief, he organized an excavation to find the library, which Ezio Auditore ultimately discovered. From 1511 to 1512, Ezio stayed in Constantinople to recover the keys to Altaïr's library, which subsequently led to him opening it. However, the library was empty, except for Altaïr's remains, a sixth key, and Altaïr's Apple of Eden.
Weary of his life as an Assassin, Ezio chose not to take the Apple from the library. However, the Apple began to glow and Ezio began to speak directly to Desmond as Minerva had. Ezio asked Desmond to make sense of the questions that had plagued him, and to make the suffering he had endured worth something. Desmond's image then appeared through the Apple.
The Templars' search
In 1722, the pirate Bartholomew Roberts, one of Aita's reincarnations, also known as a 'Sage', discovered through visions of his previous lives the existance of the Grand Temple and Juno's imprisonment in it. During Roberts' last moments, he expressed his desire to visit Juno at the Grand Temple, confusing his killer, former pirate and Assassin Edward Kenway, before requesting Edward to destroy his body once gone in order to prevent the Templars from gaining anything from it. On Edward's later life, the Assassin began to write a journal, in which he collected his research on different Temples scattered around the world, including the Grand Temple.
In 1735, Grand Master of the British Templars Reginald Birch obtained Edward Kenway's journal by killing the Master Assassin, burning his Mansion, abducting his daugter, Jennifer Scott, and adopting Edward's son, Haytham Kenway, in the process. Locating the Temple on the New World thanks to the journal, Reginald gave fellow Templar Lawrence Washington the mission to establish a Templar network in America and to become Birch's ears and eyes in the Colonies.
In 1754, Haytham was assigned by Birch the mission to come to America with the Grand Temple's key, recently stolen by killing the Assassin Miko, and to seek the entrance to the sanctuary, believing it to be a storehouse for First Civilization goods and riches. After gaining the trust of the warrior Kaniehtí:io, he was guided to the Temple's door, but without an Apple of Eden, Haytham was unable to open it. Deterred, he ordered his brethren to abandon exploring the site and focus instead on spreading their Order through the Colonies.
However, led by Charles Lee, his fellow Templars ignored his order and came to Kanatahséton to demand the location of the Temple, but were denied. Along the way, Lee assaulted Haytham and Kaniehtí:io's illegitimate son, Ratonhnhaké:ton, who returned to find his village destroyed, convinced it had been Lee who had done it.
When he came of age, Juno communicated with Ratonhnhaké:ton, instructing him to join the Assassins to prevent the Templars from ever attempting to breach the sanctuary. In 1782, Ratonhnhaké:ton, now the Assassin Connor, killed Lee and took the key as a memento. Juno then instructed him to hide the key, and Connor buried it over the grave of his namesake, Connor Davenport, on the hill overlooking the Davenport Homestead, securing the Temple. He later learned his people, who had protected the Temple for generations, had chosen to migrate west, as their land had been sold by the new American government.
- "That ominous date fast approaches. December 21st, 2012. None of us know what it'll bring - only that this is where they want us to be when it does."
- ―William Miles, on the Temple and the impending 2012 disaster.[src]
From there, Desmond opened the Temple's gates with Ezio's Apple of Eden, activating a large portion of its equipment in the process. As Desmond, William, Shaun Hastings and Rebecca Crane investigated the Temple, they found a large gate made of light that protected the Eye.
After this, Desmond was forced into a fugue state of the Bleeding Effect by Juno and was subsequently placed into the Animus to find the key, through reliving the memories of his ancestors Haytham and Connor.
Meanwhile, Shaun realized that the Assassin team needed three power sources to fully reactivate the Temple, otherwise opening the door would be of no use. Over time, Desmond recovered the power sources to activate the whole mechanism of the Temple, and with each source plugged in, Desmond witnessed visions from Juno explaining the solutions created by the First Civilization to prevent the solar flare and save the planet.
Through the memories of his ancestors, Desmond obtained the key and recovered the power sources, accessing the Eye. In that moment, Juno appeared to the Assassins once more, urging Desmond to activate the Eye. However, Minerva, who had secretly ordered a second Eye constructed, suddenly appeared as well, telling Desmond to do the opposite.
She explained that if Desmond did as Juno asked him to, the world would be saved, but at the cost of his life and Juno's release from imprisonment. Following this, Minerva showed Desmond that if he refrained from activating the Eye, the Sun would once again destroy the world, but he and many other humans would survive. Additionally, Desmond would eventually become a religious figure that would rebuild the world, but upon his death, his ideals would be mistranslated and spark religious conflicts again, effectively causing history to repeat itself.
Believing that humanity had a chance at defeating Juno, Desmond made his choice and activated the Eye, telling William, Shaun and Rebecca to leave and prepare for the new struggle. The world was indeed saved, but Desmond had perished and Juno was set free, who promised to "play [her part]". Several hours later, Abstergo Industries found the Grand Temple's location and dispatched a team, led by Case Fisher. There, they found and retrieved Desmond's body, stripping him of his backpack and his Hidden Blade, which was broken into pieces and taken to Abstergo along with the rest of his belongings.
- The entrance to the Grand Temple was located in the north of the Frontier within the Black Creek region, within a cave that was once the head of Minerva's statue, which crumbled during the Toba catastrophe. Over time, the statue's remains eroded and became little more than a massive rock edifice, with a tunnel carved out to access the Temple's entrance.
- It was possible to visit the entrance while reliving Connor and Haytham's memories, though the door was closed.
- In The Tyranny of King Washington the entrance is absent from the cave.
- The shape of the temple from the hologram in Assassin's Creed: Revelations changed to become much larger and sectioned off in Assassin's Creed III.
- According to The Art of Assassin's Creed III, the three sections of the Grand Temple are respectively meant to be a computer server, sleeping quarters, and a research facility.
- On the barrier sealing off the Temple's inner chamber, the symbol consists of an ouroboros surrounding a tetractys.