Assassin Seals were round, stone seals that each represented a legendary Assassin, and bore their characteristic weapon. Totaling six in number, the seals were required to gain access to the Armor of Altaïr, which was locked in the Sanctuary beneath the Villa Auditore in Monteriggioni.
During his journey across Italy, Ezio Auditore da Firenze retrieved the seals by traversing several Assassin Tombs and taking the seals from the sarcophagi of the Assassins. Once recovered, he placed the seals at the pedestals of the corresponding statues in the Sanctuary.
Each correct placement caused one of the bars that prevented him from gaining the Armor of Altaïr to retract. Once all seals had been brought to the Sanctuary, Ezio obtained the armor of the legendary Altaïr Ibn-La'Ahad.