Nexus

"If you mean to ask what it is you now see - it is known as the Nexus. From here, probabilities are calculated so that the proper path may be chosen."

- Juno explaining the Nexus to Ratonhnhaké:ton.

The Nexus was a disruption in time from where probabilities were calculated, to which the First Civilization had access. It was used by the First Civilization to predict the "proper path" for individuals or to speak with individuals from the future. The Nexus could be entered by activating a Crystal Ball or by achieving a Synch Nexus with one's ancestors inside the Animus.

The Nexus was entered by the Mohawk Indian Ratonhnhaké:ton by activating his tribe's Crystal Ball in 1769. He was greeted by Juno, who informed him that maintaining his proper path would lead to the destruction of his village. She instead directed him to become a member of the Assassin Order, knowing that this path would lead to him obtaining the key to unlock the door inside the Grand Temple. Ratonhnhaké:ton later entered the Nexus again in 1782 after he obtained the key, and Juno directed him to hide it where nobody would look for it, knowing that his descendant Desmond Miles would eventually find it.

In 2012, after Desmond Miles had fallen into a coma and his consciousness fell into the Black Room of the Animus, Desmond was told by Clay Kaczmarek that in order to regain his consciousness and prevent the memories of his ancestors from overlapping with his he needed to achieve a Synch Nexus; relive all memories of his ancestor inside his DNA. Desmond then proceeded to relive the remaining memories of his ancestor Ezio Auditore da Firenze in the Animus, and was transported to the Nexus, where he was greeted by Jupiter. Jupiter then explained and showed him the final days of his race, and guided him to go to the Grand Temple, after which Desmond regained consciousness.