Masyaf Key

The Masyaf Keys, also referred to as the seals, or keys of Altaïr, were a collection of six First Civilization Memory Seals containing information and memories from the Grand Master of the Assassin Order Altaïr Ibn-La'Ahad, their original owner. When brought together, the keys would grant access to Altaïr's library, in the fortress of Masyaf, which was desired by both the Assassins and the Templars during the early 16th century.

Altaïr's discovery
Following the death of his wife and 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, which he had in his possession. He retrieved these artifacts and hid them.

Altaïr's research discovered that the keys contained messages, though he did not know to whom they were intended.

In 1257, whilst Masyaf was about to be besieged by the Mongols, Altaïr passed the keys and his codex on to his guests, Niccolò and Maffeo Polo, who promised to hide the keys. They escaped from the Mongols with the help of Altaïr's son Darim, and safely arrived in their home of Constantinople, where they hid the keys and formed an Assassins Guild.

Ezio's acquisition
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 mid 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 encocded onto the key during his own lifetime. In time, Ezio recovered all five keys, including the one which the Templars had in their possession and with them, returned to Masyaf in order to open the library. Inside, he found no books or weapons as he and his Templar enemies had believed they would find, but the skeleton of Altaïr holding a sixth and final key, showing the final moments Altaïr's life; revealing the fact that Ezio's Apple and Altaïr's were not one and the same, as he had previously believed.

Trivia

 * 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.