Assassin's Creed Limited Edition Art Book, The overall story within Assassin's Creed is set in September 2012 AD. Desmond Miles, a bartender, has been kidnapped by unknown people (Abstergo) prior to the start of the game, and is brought to a building belonging to Abstergo Industries, where researchers are working on a project involving a machine called the Animus. The Animus is able to extract memories from the DNA of the user, passed on from descendant to descendant, allowing the user to replay those memories as if he were there himself. Desmond was "chosen" for the project due to his relationship to his ancestor Altaïr Ibn La-Ahad (at-ta'er in Arabic meaning "Flying One" and his last name meaning "Son of None"), a member of the Assassins Order during the Third Crusade of the Holy Land; the researchers express interest in understanding more of how the Assassins worked. Though initially Desmond's subconscious rejects the memories of Altaïr, he eventually learns to accept them and is able to proceed to follow Altaïr's actions through the Animus.

The memories of Altaïr that Desmond experiences start in the year 1191: Richard I of England has just recaptured the port city of Acre from the Saracens. With a base of operations established, the Crusaders prepare to march south. Their true target is Jerusalem, which they intend to recapture for Christianity. However the Saracen forces are massing in Arsuf, intending to ambush the Crusaders and prevent them from reaching Jerusalem. These war maneuvers have left the rest of the Holy Land wide open. While Richard and Saladin battle one another, the men left to govern in their stead have begun taking advantage of their newfound positions of power. Exploitation, manipulation, and provocation rule the day.