Library of Altaïr Ibn-La'Ahad

Altaïr's library was a hidden library beneath the fortress of Masyaf containing hundreds of books full of wisdom and knowledge gained from the Apple of Eden by legendary Assassin, Altaïr Ibn-La'Ahad, and hiding a powerful weapon.

Creation
Sometime before 1257, legendary Grand Master of the Assassin Order, Altaïr Ibn-La'Ahad had a library build over the gardens of Masyaf. When finally complete, the library contained all the knowledge and wisdom Altaïr had gained from studying the Apple. More importantly however, Altaïr had a weapon within his library, a weapon capable of ending the war between the Assassins and Templars.

Wanting to keep the content of his library safe from the hands of the Templars, Altaïr had the library locked up, with five keys being the only way to reopen the library. During the Mongol siege of Masyaf, Altaïr left the keys in possession of Niccolò and Maffeo Polo, who later hide them in Constantinople.

Reopened
By 1511 the Templars and Assassins sought all five seals to discover the weapon locked within the library. Assassin Ezio Auditore was able to recover all of the seals before opening the library and discovering it's content.