It is a book written by Oliver Bowden about the adventures of Altair, the protagonist of the Assassin's Creed saga.

The Brotherhood is an ancient brotherhood, established centuries before Ezio Auditore discovered he was a member, and everyone knows the name of Altair, one of the most legendary Master Assassins.

But for decades, a thick aura of mystery had hovered around his life. At least until Nicholas Polo, in 1257, decided to reveal its history. "Eighty years ago, a bright August day just like this one" -- so begins the extraordinary tale that Niccolo', father of the famous Marco, gives his brother from the dizzying heights of the fortress of Masyaf, the stronghold of the Assassins in Syria.

Eighty years earlier, from that very spot, the lookout had spotted Saracen ships coming to wipe out the Brotherhood, a dangerous obstacle to the Sultan's aims. That event had prematurely orphaned Altair Ibn-La'Ahad, who was therefore welcomed at a very young age among the Assassins, of whom he soon became the most skilled, reckless and proud member. So much so as to break the Creed. For such great guilt there was only one possible atonement, only one test of loyalty: to go on a secret mission and destroy nine bitter enemies.