72

The number 72 plays a significant role to the modern day Assassins during October, 2012. It is used as the password to gain access to the Colosseum Vault, where it must be said aloud.

History
As evident in the Scrolls of Romulus, the earliest known user of the number 72 as the password to the Vault was Marcus Junius Brutus, circa 45 B.C. The next known person to open the Vault was Ezio Auditore da Firenze in 1507, to seal the Apple of Eden within.



It is known, due to Desmond's vision of Ezio in the sanctuary, that Ezio later returned to the Villa Auditore at an unknown date to leave behind the clues to the password that would allow the Assassins of the future to access the Vault and obtain the Apple. Ezio left the clue just behind the bookcase in Mario's study. It consisted of an etching of an equilateral triangle with nine other equilaterals within it - the same marking found on the door of the Colosseum Vault - and the numbers 1419, 1420 and 1421 which was only visible to those who possess the gift of eagle vision.

Modern day discovery
When the group of Assassins first arrived at Monteriggioni, and gained access to the sanctuary, Desmond notified the rest of the team that the numbers 1419, 1420 and 1421 were visible to him in eagle vision just at the top of the stairs leading to the sanctuary. After much thought, the Assassins arrived at the conclusion that they were probably dates.

After discovering the location of the Apple through the use of the Animus 2.0, the Assassins pondered on how to access the Vault. Rebecca attempted to analyze the previous Animus sessions to uncover a means as to how the door to the Vault could be opened, however her work was cut short due to a power failure. As the Assassins waited in the dark and contemplated their next move, Desmond remembered the markings he had encountered when he had first opened the entrance to the sanctuary. Calling the team's attention to the numbers again, Shaun then discovered the significance of the numbers 1419, 1420, and 1421 and explained them to the rest of the team.

"The Tetragrammaton. The 72 names of God. You see? They're all contained within three verses: Exodus 19 through 21. And, get this, you'll like this. If you arrange the four Hebrew letters in God's name within an equilateral triangle, their numerical values add up to the same number: 72."

- Shaun Hastings explaining the password to the other Assassins.

Having obtained the password, the Assassins left the sanctuary, and headed for the Colosseum. As Desmond made his way through the ruins of the Colosseum and the path of the Lair of Romulus underneath, Lucy realized that there were 72 days until the Abstergo satellite launch. Wondering if it was a coincidence, Desmond dismissed this, stating that; "Someone probably wanted to make sure we get the password right". He eventually emerged in the Santa Maria Aracoeli with the other Assassins. After a free-running puzzle, Desmond activated an elevator that took them down into Juno's Temple where the door to the Vault was located. In front of the door, Desmond said aloud "72", thus the Vault opened, and the Assassins entered.

Trivia

 * Both Rodrigo Borgia and Maria Auditore died at the age of 72.
 * Lucy mentions that the date is October 10th, 2012 and that the Abstergo satellite launch will take place in 72 days time, on December 21st, 2012.
 * Shaun Hastings mentions that that construction on the Colosseum started in the year 72 A.D. The Assassins found the that entrance into the Temple of Juno underneath the Santa Maria Aracoeli was hidden under the Colosseum.
 * William M. mentions in an e-mail to Shaun Hastings that the team in Osaka was scheduled to make contact with headquarters in 72 hours and that they went "dark".
 * Giovanni Mocenigo was the 72nd Doge of Venice.
 * The Latin Rule, the Creed of the Templars written by Hugh de Payns, had 72 clauses.
 * At the end of Assassin's Creed: Brotherhood, Shaun mentioned that a Phrygian Cap and a Masonic Eye came together at one place, but he froze before he could tell where. It is actually on the Declaration of the Rights of Man and of the Citizen of France, which was approved in 1789. Coincidentally, 89-17=72.
 * The triangular figure is also known as a tetractys, and features in the Divine Science chapters leaked from Project Legacy.
 * In an arch on a bridge in the famous Leonardo da Vinci painting, the Mona Lisa, it seems to have the number 72.

Source
Assassin's Creed: Brotherhood