72

The number 72 played a significant role to the modern day Assassins. Most notably, it was used as the password to gain access to the Colosseum Vault during the retrieval of the Apple in October 2012.

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.E. The next known person to open the Vault was Ezio Auditore da Firenze in 1506, to seal the Apple of Eden within.

Due to Desmond Miles' vision of Ezio in the Sanctuary, it is known that Ezio later returned to the Villa Auditore to leave behind the clues to the password that would allow future Assassins to access the Vault, and obtain the Apple.

Ezio left the clue on the Sanctuary staircase, just behind the bookcase in his uncle 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 were only visible to those who possessed the gift of Eagle Vision.

Modern-day discovery
"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 explaining the password to the other Assassins.

When the group of Assassins first arrived at Monteriggioni, and gained access to the Sanctuary, Desmond noticed and read out the numbers written into the wall. Shaun Hastings posited them to indicate years, though he could not think of their significance to each other.

After discovering the location of the Apple through the use of the Animus, the Assassins pondered on how to access the Vault under the Colosseo. Rebecca Crane discovered that the door required a password, but a power failure cut short their attempts to discover it.

As the Assassins waited in the dark and contemplated their next move, Desmond remembered the markings, and pointed them out. Shaun finally discovered the significance of the numbers and explained them to the rest of the team; pointing out the 72 names of God found in Exodus chapter 14, verses 19 through 21.

Having obtained the password, the Assassins left the Sanctuary, and headed for the Colosseo. As Desmond made his way through the ruins of the Colosseum and the path of the Lair of Romulus underneath, Lucy Stillman realized that the current date, October 10, was exactly 72 days away from the Abstergo Industries satellite launch in December 21.

Though she wondered aloud if this was more than a coincidence, Desmond dismissed her unease, stating that; "Someone probably wanted to make sure we get the password right."

The team eventually arrived at Juno's Temple, where the door to the Vault was located. After briefly wondering if the door would understand English, Desmond spoke "72" aloud, thus opening the Vault and allowing the Assassins to enter.

As Desmond activated the Apple, Juno told him that his journey would begin on the 72nd day before the awakening.

Trivia

 * Both Rodrigo Borgia and Maria Auditore died at the age of 72.
 * Shaun Hastings mentions that the construction on the Colosseum started in the year 72 C.E.
 * William Miles mentions in an e-mail to Shaun that the team in Osaka was scheduled to make contact with headquarters in 72 hours, but 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.
 * During the conclusion of Assassin's Creed: Brotherhood, Shaun mentions that a Phrygian Cap and a Masonic Eye came together in only one place, though he is frozen before he can continue. This one place 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.
 * PL-Allegro.png.]]The triangular figure is also known as a tetractys, and features in the Divine Science chapters of Assassin's Creed: Project Legacy.
 * An arch on a bridge in the famous Leonardo da Vinci painting, the Mona Lisa, appears to display the number 72.
 * In Assassin's Creed: Revelations, Ezio can train a total of 72 recruits to the rank of Assassin, not including Rhodes.
 * In Leonardo Da Vinci's sketch "Vitruvian Man", the space between the man's lower arm to upper leg has an angle of 72 degrees.
 * Desmond Miles was born on the 72nd day of the year 1987.
 * According to the Assassin's Creed II database, San Gimignano had 72 towers in its heyday.