- "If our experiments with Desmond in the Animus aren't going well, you will remove him from Abstergo. Take him somewhere he will feel comfortable divulging his secrets. Your Assassins should do the trick."
- ―Warren Vidic to Lucy Stillman.[src]
Project Siren was a Templar plan to extract more information out of Subject 17, Desmond Miles. While Abstergo Industries was trying to locate him for the Animus Project, its overseer Warren Vidic realized that Desmond would not willingly co-operate with their plans for him, and concocted a scheme to relocate Desmond to a seemingly safer environment.
Warren and his assistant Lucy Stillman decided that Desmond would have to leave the laboratory in Abstergo's Rome facility, in the eventuality that progress through his genetic memories would not be quick enough. From there, Lucy would contact Shaun Hastings and Rebecca Crane, two Assassins, and take Desmond to their hideout.
Both of the Templars hoped that Desmond would feel more at ease amongst the Assassins, thus allowing him to access crucial memories more easily; particularly the ones that Abstergo desired. Lucy was then to contact Vidic once the Assassins had located the Apple of Eden.
However, this plan would ultimately fail, due to the interference of the Isu entity Juno, who knew the true danger Lucy posed. When Desmond arrived at the Colosseum Vault, Juno influenced him into killing Lucy with his Hidden Blade as soon as he touched the Apple of Eden; insisting that he "knew very little", and that she would guide him.
- The project's name was derived from the nature of the siren, a creature of Greek mythology. Sirens would lure sailors to their death by singing in a seductive manner, leading their boats to crash on the rocks and the entranced sailors to drown in the wreckage.
- Assassin's Creed II (first appearance)
- Assassin's Creed: Brotherhood
- Assassin's Creed: Revelations (mentioned only, first referenced by name)