- "Here's the problem. Your brain is hash. Too many ghosts in your head, too many voices. So how do you fix that? You claw your way back into the stored data, you find unfinished memories, and you crack them open. Finish what you started, until your ancestor has nothing left to show you. That is a synch nexus."
- ―Clay Kaczmarek to Desmond Miles.[src]
A Synch Nexus was a moment achieved after an individual had fully experienced the genetic memories of one or more of their ancestors, with nothing left to observe. It allowed an individual access to the Nexus and was necessary to avoid the harshest consequences of the Bleeding Effect.
In 2012, after retrieving Ezio's Apple of Eden, Desmond Miles fell into a coma. Returned to the Animus to sustain his consciousness, Desmond "awoke" in the Black Room, the Animus safe mode, where he met the visual representation of Animus Project Subject 16, Clay Kaczmarek.
Clay eventually told Desmond that the only way to escape was to achieve a synch nexus, the complete conclusion of his ancestors' lives, which were threatening to permanently bleed into Desmond's own memories and personality.
Upon completing these memories, Desmond achieved a synch nexus, and was pulled into the Nexus. Once there, Jupiter, a member of the First Civilization, spoke with him about the Grand Temple, and the First Disaster.