- Niccolò: "Artifacts?"
- Altaïr: "Of a kind. They are keys, each one imbued with a message."
- ―Niccolò Polo and Altaïr Ibn-La'Ahad on the Masyaf keys.[src]
The Masyaf Keys, also referred to as the seals or keys of Altaïr, were a collection of five First Civilization Memory Seals containing information and memories from the Mentor of the Levantine Assassins, Altaïr Ibn-La'Ahad, their original owner.
Following the death of his wife and younger son, and his deposition at the hands of Abbas Sofian, Altaïr entered into exile in the Assassin fortress of Alamut. During this time, Altaïr was directed to six Memory Seals by the Apple that he had in his possession. He retrieved these artifacts and hid them.
Altaïr's research discovered that the seals contained messages, though he did not know to whom they were intended. He would later imbue the six seals with his own memories, and make use of five of them as the keys of his library.
In 1257, whilst Masyaf was about to be besieged by the Mongols, Altaïr passed the five keys and his Codex to his guests, merchants Niccolò and Maffeo Polo, who promised to hide them. They escaped from the Mongols with the help of Altaïr's son Darim, safely arriving in their home city of Constantinople, where they hid the keys and formed an Assassins Guild.
In 1510, Ezio Auditore da Firenze, the Mentor of the Italian Assassins, learned of the existence of Altaïr's library and its keys after reading a document left behind by his late father, Giovanni. Curious and driven by a desire to obtain answers about his Order, Ezio left Rome for Masyaf.
Ezio arrived in Masyaf in early 1511, at which point Niccolò Polo's journal, containing information on the keys, had come into the possession of the Templar Leandros, the captain of a group of Byzantine remnants. After a long struggle, Ezio was able to kill Leandros and obtain the book.
Ezio journeyed to Constantinople, where he started his search for the keys, eventually finding one underneath Niccolò Polo's old trading post, which, at that point, was inhabited by the Venetian bookseller Sofia Sartor. With her assistance, Ezio was able to decode a map showing the locations of all keys in Constantinople.
With every key that Ezio found, he found himself reliving a significant moment of Altaïr's life, which the Syrian Assassin had encoded onto the key during his own lifetime. In time, Ezio recovered all five keys, including the one that the Templars had in their possession, and returned to Masyaf in order to open the library.
Inside, Ezio found no books or weapons as he and his Templar enemies had believed they would find, but the skeleton of Altaïr holding his sixth and final seal. This showed him the final moments of Altaïr's life, and revealing that Ezio's Apple and Altaïr's were not one and the same, as he had previously believed.
Thus ending Ezio's journey, he symbolically stripped himself of his battle gear to renounce his life as an Assassin.
Altaïr's Seals were then returned to Constantinople upon Ezio and Sofia's return to the city after the revelation in Masyaf. All six seals were then hidden by Ezio in the chamber beneath the bookshop, within the Yerebatan Cistern.
- The markings on Memory Seals are similar, if not identical, to a symbol shown in the Vatican Vault at the end of Assassin's Creed II. When Minerva speaks of the Temples, she shows Ezio an image of a step pyramid, above which is a symbol resembling one of the keys.