In the year 1190, the wars of the Third Crusade engulfed the Holy Land, and Crusaders clashed with Saracens for the control of the Holy City, Jerusalem.

Altaïr Ibn-La'Ahad, a renowned Master Assassin of the Assassin Order, arrived at Alep from an arduous journey and found it under attack by the sworn enemies of the Assassins, the Knights Templar. Left with no choice but to repel the attack, the Assassin defeated many of them, even killing a low-ranking captain before the attack was halted.

Afterwards, tasked by Rashid ad-Din Sinan, the Mentor of the Levantine Assassins, Altaïr was sent to find and retrieve a sacred object known as the Chalice, which was said to have the power to unite all the factions under one flag of whichever side possessed it, ending the Third Crusade in victory for either the Crusaders or the Saracens. Setting off immediately, Altaïr embarked on his new quest.